The Serve
For beginners, I recommend you mimic Jimmy Connors' serve. It's a simple, straightforward stroke that will help you develop a reliable serve. It also makes it easy to hit the serve flat, with topspin, or with slice. If you're an intermediate player, going on advanced, then I would advise you to look at Pete Sampras' serve. It's a beautiful, classic stroke.
John McEnroe's serve was awesome to watch, but it was a unique stroke; I don't think we'll ever see a top pro hit one like his again. In his autobiography, he explains that the deep waist bend at the beginning of his serve was originally a way to loosen up his back when he played at Stanford. Ivan Lendl had a nice service motion, but I think Sampras had a better one. Lendl did have a great looking follow-through, his left forearm thrown horizontally across his midsection in order to brake his body and exaggerate the snap of the racquet into the serve. Stefan Edberg had too high a toss for most players to imitate; it required a pause in his service motion that I see no reason to copy. Goran Ivanisevic had a great serve, but you better be in darn good shape if you're going to try it. Andre Agassi has a solid serve -- not great, but not a bad one to copy, and it's not as physically demanding as Sampras' serve. Boris Becker's serve was unique to him, I think. Becker's follow-through was odd; the racquet would end up pointing straight down on the right side of his body. He didn't naturally follow through across his body like most servers. I'm surprised he didn't have more injury problems during his career because of that. If you're going to adopt a Becker-style serve, where the back foot crosses over the front one and steps into the court, you're better off copying the smooth, fluid stroke of Yannick Noah.
On the women's side, Martina Navratilova has the classic serve. The newer players serve faster, but none of their serves are as effective as Martina's was in her prime. There's more to serving than power; placement, spin, and disguise are equally important. Many of today's top women use serves similar to Steffi Graf's, which itself is similar to Ivan Lendl's. If you don't copy Martina, copy Steffi. One serve not to copy is Gabriela Sabatini's. I remember Sabatini hitting a 49-mph serve at the U.S. Open. That is just unheard of. Sabatini is a beautiful woman (as beautiful as Kournikova but more exotic), but her serve is an ugly duckling. I'm sorry, Gaby.
The forehand
If you're a beginner, I would use a semi-western grip and copy Mats Wilander. His stroke enabled a very natural, consistent forehand with a high margin of error. He hit his forehand with an "open" stance; that is, the line of his hips was mostly parallel to the net. But he turned his shoulders, and that's the important thing. Traditional tennis wisdom said to hit the forehand with a "closed" stance, meaning that you would turn your whole body to the forehand side so that the line of your hips would be perpendicular to the net. Stan Smith hit the classic forehand, turning his body sideways, bringing his racquet around in a loop, and striking the forehand with a beautiful, fluid motion that left the racquet properly elevated, its handle near Smith's left shoulder, and his shoulders turned parallel to the net at the conclusion of his shot. The closed stance, I think, was more important in the days of wooden racquets. But many great players of what you might call the "graphite era" have used an open stance on the forehand. Jim Courier, for example, wouldn't bring his hips around. But he would turn his shoulders almost 90 degrees to the net, and his whole upper body would rotate into the shot. On his follow-through, his shirt would have striations in it like a twisted towel. This is what makes the open stance forehand viable. With modern racquets, you don't have to turn your hips; the revolution of your shoulders gives you all the power you need. Andre Agassi, who hits as hard a forehand as anyone, uses an open stance.
Boris Becker's big forehand was sort of an exaggerated version of Wilander's. It was a solid shot, but try it first with a semi-western grip; the western grip is not one for beginners. Pete Sampras had a great forehand; no one hit running forehand winners better than him. His forehand is an interesting contrast to Agassi's. Sampras' forehand depended a lot on muscle memory; he didn't throw a lot of last-second adjustments into his shot, and it didn't include much wrist motion. Agassi has a great forehand, but it would be tough to imitate because a lot of its greatness is the result of Agassi's phenomenal natural ability and timing. Sampras' forehand was tailor-made for a midsize racquet, while Agassi's forehand almost demands an oversized one. It would definitely be easier, though, to adapt Sampras' forehand to an oversized frame than it would be to adapt Agassi's to a midsize. Agassi needs that big hitting area, because he hits a fairly "wristy" forehand, and he'll change his shot at the last second more often than some other players. For most players, I think the Sampras forehand will be more reliable but less adaptable and, you might say, less whimsical than Andre's.
Ivan Lendl had the best forehand of his time, but I don't think it translates well to modern tennis. It had a big wind-up that was lethal in the '80's, but I think it would be too hard to time when returning shots hit as hard as they are now. Of course, Lendl dominated some big hitters during his years at the top, so I might be wrong. It certainly was a dramatic shot; people often didn't acknowledge that, because it was hit by a fairly un-dramatic player. At its best, Mary Carrillo accurately said that "a forehand simply could not be better struck" than Lendl's. Kevin Curren (the monster server who Becker beat in the '85 Wimbledon final) had an extremely wristy variant of the Lendl forehand.
Steffi Graf had one of the all-time-great forehands, but it was definitely an individual stroke; she always looked like she was hitting it late.
Chris Evert and Jimmy Connors had very similar forehands: very simple and straightforward, utilitarian, nothing fancy. Chris Evert's consistency was simply unreal, especially considering that she didn't hit moonballs; she used a little topspin, but she mostly drove the ball, not clearing the net by as much as most baseliners. Her forehand is a good one for beginners using an eastern forehand grip; more advanced players, though, should go for a looping preparation to give their shot more topspin.
I thought Gabriela Sabatini had a fine forehand. Some purists didn't like her groundstrokes because she often hit them off her back foot, as if she were falling backwards. But she took such a big swing that she often would have drilled her shots into the opposite fence if she had put her weight into them. She hit a big topspin forehand; it wasn't heavy on pace, but it had nice consistency.
Stefan Edberg had a funky-looking forehand, sort of like a Lendl forehand modified for a continental grip. Mary Carrillo tells a great story about Edberg seeking out the tennis statistician Leo Levin and asking him, "Tell me something about my game that I don't know." Levin gave a very sagacious reply: "The numbers on your forehand are good." Analysts often said that Edberg's backhand was his better shot; they figured that, since his backhand was such a smooth, elegant stroke, it must be more effective than that odd-looking forehand. But the fact was, Edberg made that forehand work; he hit a higher percentage of passing-shot winners with the forehand than with the backhand! Nonetheless, I wouldn't advise anyone to copy Edberg's forehand. It worked because Edberg was a sublimely gifted athlete, the Swedish version of John McEnroe. Edberg was so classy that the tennis establishment named its sportsmanship award after him.
The Backhand
The backhand is the Edberg shot you should copy. On the topspin backhand, he had great preparation and fluid execution. It was one of the best-looking shots tennis has ever seen. He also hit an excellent slice backhand, though most recreational players won't be skilled enough to cut down on the ball as sharply as Edberg did. He often used his slice to come to net, and he wanted to put lots of underspin on the ball to keep its bounce low, forcing his opponent to hit up on the passing shot. Mats Wilander also hit his slice backhand with a long high-to-low sweep that most weekend warriors would be unable to time properly. But if you make the backswing slightly shorter and the stroke slightly slower, you should be able to come up with a reliable Edberg/Wilander-type slice backhand.
Pete Sampras had a magnificent one-handed backhand which is also a great model to copy. In fact, the mechanics of the Sampras topspin backhand may have been even better than Edberg's. Tim Henman, the great Brit hope, also has a nice backhand which appears to have been modeled after Edberg's.
I think Boris Becker relied a little too much on his strong forearms on the topspin backhand; it worked for him, but I think most players would have unsatisfactory results with it. Becker had a fairly simple slice backhand, a basic chop at the ball which was adequate but not spectacular. Lendl's slice backhand was fairly simple too, but he put more drive on it than Becker did.
Ken Rosewall had what is generally considered to be the finest slice backhand in tennis history. He hit it so well that he didn't need a topspin backhand. I've seen his stroke, and it looks a little more complicated to me than most slice backhands. It seems as if he rolled his wrist on the stroke to get the racquet face into just the right angle when it made contact with the ball. I've read that his consistency with the stroke was astounding, but I suspect that had more to do with his natural abilities than with an inherent superiority of the stroke itself.
Ivan Lendl's topspin backhand deserves its own paragraph; it was great. Lendl's topspin stroke was a huge low-to-high swing; the racquet head would be traveling at an unusually steep vertical angle when it made contact with the ball. Lendl generated power on the shot not with his arm, but with the rotation of his shoulders. The result was an amazing combination of spin and pace. Lendl suffered some shoulder problems late in his career which may have been the result of that mighty swing, which threw his arm powerfully away from his body. Lendl would generally follow through across his body, but sometimes, on low balls, his arm would follow through straight ahead of him. I remember a big backhand pass he hit to break Becker's serve in the '89 U.S. Open final. Becker had hit a volley low to Lendl's backhand. Lendl dropped to where his left knee was just a couple inches above the court, and he hit one of those line-drive backhands; at the conclusion of his follow-through, his right arm was extended straight out in front of him, pointing in the same direction as the shot. (Lendl was very good at staying down when returning low balls. It's tempting to pull up on topspin shots, in an attempt to transfer your body English into the shot, but it often results in a mis-hit, since your body, the racquet, and the ball are all in motion. Keeping your upper body at about the same height throughout the shot will produce more consistent results.) Lendl's main vulnerability on the backhand was a result of the very small face on his racquet. He didn't have a big sweet spot to work with; his timing had to be nearly perfect, and that wasn't always easy when balls were coming at him at over 100 miles an hour.
Gabriela Sabatini had a big, dramatic one-handed topspin stroke that was a delight to watch; she particularly excelled at the up-the-line pass. Steffi Graf also had a beautiful one-handed topspin backhand, though she didn't use it much; she preferred to cut under the backhand. Graf's slice backhand showed what a talented player she was; her timing was amazing. On her preparation, her left hand would be cradling the throat of the racquet, as it should have been, but the racquet would be pointing upside down behind her! Then she would whip the head up and slice it back down into the shot, flattening out her follow-through across her body. The result was potent underspin which kept the bounce extremely low, preventing her opponents from taking advantage of the shot. Chris Evert tried to one year at the Australian Open, going relentlessly to Graf's backhand wing in the second set, but Graf squeaked it out.
Most two-handed backhands come from more or less the same mold; you don't find a whole lot of variety there. Michael Chang, for example, is about 9 inches shorter than Todd Martin, but their backhand strokes are nearly identical. Most two-handers keep it simple: take the racquet back low, and use very little wrist motion when swinging the racquet up. You can copy just about any two-hander on the pro tour, on the men's or women's side, and you'll wind up with about the same shot. Andre Agassi is an exception; he often uses a little wrist flick which gives him greater disguise and variety. If you're a beginner, go with a basic two-hander, but if you're moving up, try copying Andre. Agassi's stroke is a little more complicated than the others, but I think you'll find it rewarding if you try to imitate it.
There have been a couple great players who had very distinct two-handed backhands. Jimmy Connors, for example, had a stroke that was unique to him. Arthur Ashe compared it to Stan Musial hitting a line drive. Jim Courier also had a two-handed shot that was often compared to a batter's swing. While both of these players had great success, I wouldn't recommend that you imitate their backhands. There are some strokes that only seem to work for their inventors.
Chris Evert had a backhand that was unlike most two-handers you see today. Having grown up in the era of wooden racquets, Evert drove through the shot more than most current players do. I would love to see a contemporary player imitate her backhand; I think it would still work today. Her technique was subtly different from Connors; she could put more topspin on the ball and achieve greater consistency. That's why I recommend Evert's backhand but not Connors'.
Volleys
The great volleyer who first comes to mind is John McEnroe. No one was more gifted at the net. His fantastic hand/eye coordination, cat-like reflexes and nimble feet enabled him to execute volleys like no one else. His technique wasn't always by the book, though. As a rule, you don't want to let the racquet head drop on volleys; you want to bend your knees and keep that racquet head at the same level as your wrist or higher, if possible. McEnroe's skills enabled him to defy those rules more successfully than any other player, though he insists that he bent his knees more than he's given credit for. I'm not in any way taking away from McEnroe's genius, but I do think there's a better role model in the forecourt: Stefan Edberg. Edberg had natural talent nearly equal to that of McEnroe, and his technique was flawless. If you can catch his old matches on TV, there is no one better to copy on the volley.
Pete Sampras had great technique, but I don't think he had the touch of McEnroe or Edberg. (His all-around game, though, was better than anyone's since Rod Laver.) In a way, that fact should be encouraging; it shows that diligent attention to proper technique can make up for a slight deficit in talent. (When I say "slight", I mean razor-thin. Nonetheless, I don't think Sampras had the coordination and reflexes of Johnny Mac or Super Stefan, or of Andre Agassi, for that matter.) Boris Becker considered Tim Mayotte to be a great testament to the value of a strong work ethic; he said that Mayotte made it into the top ten through relentless practice, "with no talent." That's a rather harsh assessment. I don't think Becker was as gifted as McEnroe, Edberg or Sampras. I think a lot of Becker's success at the net was because of his long reach and because he came to net behind such big shots. No arguing with the results, though.
Yannick Noah could do great things with the volley, but I don't think it was because his technique was particularly special. I just think he had talent and a predilection for artistry on his shots. Boy, he hit some pretty ones. So did another Frenchman, Henri Leconte.
On the women's side, Martina was the great volleyer. Her style was so exciting and fun to watch. It's such a shame that she never got the fan appreciation that she deserved; she's getting more now, in her forties, than ever before. Better late than never, I suppose. Jana Novotna also was outstanding at the net; I was so happy to see her finally win Wimbledon and get the monkey off her back. Steffi Graf had excellent volleys and a particularly fierce overhead; it seemed like no matter how high the lob was, Graf would time it perfectly on the way down. Billie Jean King was the same way; I saw her in exhibition matches years after she retired, and she was still putting away tough overheads with ease.
Mental Game
Mats Wilander had perhaps the greatest on-court intelligence; as a match went on, he seemed to get a read for where his opponent was going to hit the next ball. He also excelled at exploiting his opponents' weaknesses on any particular day; if one part of your game wasn't quite on, Wilander would notice it, and on the big points he knew where to go.
Jimmy Connors had top-notch fire and desire; his will to win made him the tennis equivalent of Michael Jordan. At least until Pistol Pete came along. Sampras was the number one player in the world an incredible six years in a row, breaking Connors' record. (In both cases, other players briefly took over the top spot during their reigns. At year's end, though, Connors was number one from 1974 to 1978, while Sampras dominated from 1993 to 1998.)
Chris Evert had super-human focus and consistency. Steffi Graf was also extremely tough; I doubt any tennis player won more big matches while fighting injuries than Graf. Martina Navratilova seemed more fragile mentally than Evert or Graf, but that's probably just because Martina wore her emotions on her sleeve.
On-Court Demeanor
It was wonderful to watch Chris Evert and Martina Navratilova play each other, not just because of the high level of tennis, but because of the respect they had for each other and the sportsmanship they showed.
The problem I always had with Jimmy Connors was that I think he deliberately used his antics to rattle and derail his opponents. When I watch a match, I want to see high-quality tennis, regardless of who wins or loses. I don't want to see one player do everything in his power to bring down his opponent's level of play to the point where he can be beaten. McEnroe threw some inexcusable tantrums as well, but at least with him, I got the impression that he was genuinely angry about something. With players like Nastase and Connors, it seemed more calculated. If their opponent got on a roll and they felt the match slipping away, they would find something to scream about. I loved the way Connors hit the ball, but I wish he had adopted just a little of Borg's stoic but classy demeanor. Borg wasn't very expressive, and yet he wasn't the least bit dull (except perhaps on clay).
Steffi Graf was a very classy competitor. She didn't play mind games with her opponents; she didn't need to. Graf knew that the most dispiriting thing she could do to her opponent was to put the next ball in play and keep up the attack. Graf's relentless barrage of well-placed serves, big forehands, and sharply cut backhands would undermine her opponent's confidence more than any display of temper.
The Swedes were known for their on-court grace. Stefan Edberg, as I've said, had tennis' sportsmanship award named after him. Wilander and Borg were also great role models in this respect. The story goes that Borg, as a young player, threw his racquet during a match, after which his father wouldn't let him play for six months. That seems like a rather draconian punishment, but it achieved the desired effect, and Borg went on to set a great example for players all over the world.