I have been amateur bodybuilding for about 5 years and have read many books on diet and nutrition. I encourage you study and read as much as you can knowledge is power. As someone has already said bodybuilding.com is an excellent resources.
Here are a few pointers to get you started.

Eat at home! Do not go near fast food.

Do not drink alcohol. Alcohol is completely counterproductive to losing weight. One good night of drinking can change hormone levels for up to a month!

If you have a Trader Joeâ??s near you, shop there! Trader Joeâ??s carriers the most inexpensive high quality foods around, bar none.

Meal plan. Every meal you eat should contain some protein, complex carbohydrates and mono and ploy unsaturated fats.

Eat six to seven small meals a day.

Eat all the green leafy vegetables you can and lots of fruits.

A couple times a month you could treat yourself to something deliciously unhealthy (I usually get high as shit and eat a ton of Chinese food).

When I smoke I like to eat (shocking I know). I find that healthy foods taste amazing when high. There is nothing like oranges, tangerines, or grapefruit when I am high. In fact citrus fruit is my favorite thing to eat when I am stoned. Natural peanut butter is also delicious macadamia nut better is even better.

Hope that helps

edit: I almost forgot one of the most important tips, drink tons of water.