Short answer, eat the right types of foods more frequently. Read as many of these articles as you can:
http://www.stumptuous.com/category/eating/how_to_eat
Start from the bottom up. Don't be afraid to eat big after a workout, because that's when your body will metabolize food the best. Just make sure you're eating "right".
If you need to snack, eat nuts. Almonds and cashews are the best.