The key is to use good form, and not to over train your muscles. You need to let your muscles rest in between workouts. Give them 3 or 4 days to rest before training them again. Follow up each workout with a protein shake and your legs will never be the same.
Your chest muscles are a large part of your upper body. To achieve maximum results, your chest workout routine should include at least one compound exercise (to work your overall chest) followed as well as a more concentrated exercise. You can also single out either your upper chest or your lower chest if you need to.