Being an intermediate leader, I have found through my own personal trial and error experiences how to place good protection in the rock. I do admit that I do not know everything about gear placement, but I have listed some tips and included some diagrams to help with the first time leader. Do not do any leading at McConnels Mill unless its sport, You will die!...I suggest that your first leading experiences be at either Cooers Rocks or New River Gorge if your in my area. Rock does break, dont be stupid. I will have pictures up from this spring of myself leading, and setting up anchors, showing good tips and close-ups of my gear in the rock. Also, I suggest that your first lead be Mr. Clean (5.7) at Coopers Rocks, It has a good anchor at the top, but the climbing is difficult. This climb requires nuts, tri-cams and camalots.
Leading is very very fun, though it can be dangerous if you are stupid. Though most suggest taking a course on leading, most people including myself get their education from nothing more than watching people do it, and also from hands on Top-rope protected Lead Climbing. This is very helpful for learning to place gear and clips.
Now, you will need to get some gear for leading. My starting rack included a large assortment of small sized nuts (a few #1s and #2s, two #3-4s, 3-4 #5-6s, 3-4 #7s-#8s, and a few assorted #11s and #13s. With these I included a health selection of camp tricams, which can be mail ordered from thie site, Rock Creek Outfitters. I have about 5-6#.5 tricams. These are great!, also I have a large selection of other small sizes, + a few larger ones. These are a must!. They work as cams, but cost a lot less. Now finally, the money pullers, I have three Camalots from Blackdiamond, a #1, #2, and #3. I am hoping to get a #.5 and and #.75. These are no brainer placesments, however, they are expensive. Tri-cams are more tricky, however, they are really really cool, there my favorite in fact, however cleaning them can be difficult unless you know the trick (read on, it will be here soon!).
Nut placement is quite easy, however, if these are not place in the direction of the fall, it can be very bad. Remember, always place your protection for the downward pull (there are excepts but dont worry about them for now). When you fall, you will inherently pull downward on the nut, and possibly sideways. Place the nut so that it will not pop. Also, make sure that the nut is completely into the crack, not have hanging out, if you need to, use a small nut that will go deeper. Also, make sure that the nut is solid, you can tell if its soldid, furthermore, do not ever ever lower from a nut in a horizontal. Infact they are terrible for horizontals unless the rock bottlenecks. You are better off using a tri-cam in a horizontal.