The main key is to simply plan ahead with food and not resort to junk food. Oatmeal for breakfast is like 39 cents. Get a slow cooker and cook it overnight, like this: http://tnation.t-nation.com/free_online_forum/diet_performance_nutrition_bodybuilding_velocity_recipe/overnight_steel_cut_oatmeal
On Sunday’s make a big batch of chicken breasts and anything else you can pre-make. Rice is a super cheap carb source. I do generally suggest avoiding wheat products; it’s mostly junk food anyway. This keeps the cravings down and naturally removes a lot of the things that cause fat gain.
Lots of recipes in the Healthy Solid Meals / Recipes forum. Do a search for the slow cooker ones. Easy and cheap, and you can make big batches at once and pack food with you.
So, in short: focus on food selection, avoid the obvious junk, and plan ahead. I lost over 65 pounds in college (I was near obese in the early days), so it can be done.