The quads have four heads. The outer head adds most of the size and is used by keeping legs close together and toes pointed forward. The inner head is worked by having the legs further apart and toes pointed out. Nothing exhausts the body like leg training! There is nothing as pathetic as seeing a guy with a awesome upper body and chicken legs.
Just like any good leg routine, these will center around the squat. As you all know already, It is the best leg exercise out there and when performed correctly you'll be amazed at the results. Squats will help out your growth for the rest of your body also. So spend time getting down the technique on squats. Again, make sure you are going down at least to parallel.
Like the quads, the hamstrings have 4 heads also. They are best trained using curls, stiff-legged deadlifts and legpresses with the feet high on the platform. If your too tired after training quads you may want to do hamstrings first so you don't lose any intensity on them.
Im starting here with a beginner routine for those of you who are just starting leg training. The first 6 months are when you will see the best gains so be prepared for some pain. This routine will only work if you give 110%. In 6 months you will be on your way to being a quad god.
Remember, don't use a belt unless you are doing less than 6 reps.
After you have been doing that for several months and added a few inches to your legs, its time to move to the advanced routine. I have added some new exercises to continue building size and to start shaping your legs.
Good luck, and keep growing!