Attack Pattern: They follow you when you're not looking, and then stop and hide when you face them.
Basic Fighting Strategies: Avoid him. The Spin Jump might help you if you have to jump over him, because if you don't make it all the way, you'll just bounce off of him.
Advanced Strategies: He can be beaten with a cape slide, but it's pretty tough. You need enough space to take off (with the cape, of course). Once you're in the air, allow yourself to float down to the ground, and you should slide along on your belly for a few seconds. If you hit Big Boo during this time, he'll be beaten (for a lousy 200 pts.) If you hit him while in the air, you probably won't lose your cape, but you will fall.

Attack Pattern: As usual, they follow you around until you face them, and then they hide.
Basic Fighting Strategies: Eggs should kill them in either game.
Advanced Strategies: In SMW2, if you find that eggs fly straight through them, you can try facing away, and then ricocheting an egg off a wall. However, I don't think this will actually be a problem, I just haven't played the game that much.

Attack Pattern: They have a range of attacks - regular attacks and lightning orb are their favourites (neither is too powerful). They can also scream, which will cut one character's offense in half, and they can use Bolt, which causes a lot of damage.
Basic Fighting Strategies: Take these guys out first. They aren't too strong, so Mallow should probably be able to beat them with one timed hit, and Mario will definitely be able to (he might even be able to beat them with one regular hit) The reason you want to beat them first is because of their powerful Bolt attack, and their scream, which will really take the power out of your attacks.
Advanced Strategies: Pure water will kill them instantly, but it might be better to use it on the other, tougher ghosts in the crowd, since they are so weak. If Mallow is strong enough to beat them with one hit, you might want to have him take them out while Mario concentrates on the more powerful enemies. If he isn't, you might want to use him to wear down the others (especially Shadow) while Mario takes out the trash. Bolt is another possibility for Mallow.
Blocking Big Boos is quite hard. They will disappear, and then reappear right in front of you, they drift forward a bit, then pause, then suddenly make a face. You need to hit the A button just as they start to make the face.