Start with knowing exactly what your body needs for your activities. Once you know that you can eat a bit less to cut the fat, a bit more to
gain muscle.
Get a free account at
www.fitday.com and track everything that goes into your mouth for a week. Then you'll know from there where to go...more protein, more fat, more carbs...or less of them.
Overeating will make you
store fat. Undereating will make your body struggle to hold on to every ounce of it as long as possible. Eating the wrong foods for your body will not support muscle and will support fat.
What are the right and wrong foods for your body - we don't know yet, but it can be discovered with time, experimentation, and practice.