I think your best place to start would be to calculate your current caloric intake using a site such as FitDay.com. Spend a few days plugging in the foods you eat and you should come to an understanding of exactly how many calories you are actually consuming each day. Most people are really surprised on how much they actually eat and where those calories are coming from, do yourself a favor and be honest in your logging otherwise you are just cheating yourself. Once you have that information you can begin making changes to your diet.

When you have that information you can reference a caloric intake calculator and determine how many calories you have to cut in order achieve your goals. Of course these aren't 100% accurate, but they give you a general idea of what you need to do to lose the weight. Here is one from WebMD: http://www.webmd.com/diet/calc-bmi-plus

Other than that I would suggest reading up on the stickies in the nutrition and training forum for some general advice and feel free to hit us up with more specific questions.