What worked for me:
Go vegetarian for about 6 months.
Drink 1-2 myoplex shakes a day (you should be getting 100-150 grams of protein a day depending on your size/workout intensity)
DONT neglect cardio.
Edit - Eat plenty of COMPLEX carbs (try to limit, if not cut out simple carbs - ie anything processed, high sugar, or if corn meal or white flour is the main ingredient, which is a lot of stuff).