Calories in VS Calories out
Weight loss is really a simple thing. You need to burn more calories than you consume. So if your body uses about 3000 calories each day, you will want to eat 2500-2700 calories. This forces your body to use your stored fat for energy.
To figure out how many calories your body uses each day, you will need to write down everything you eat. Write everything down in a spreadsheet, and you can find nutrition facts at Nutritiondata.com or other sources. You will want to write down Calories, Fat, Carbs, and Protein for everything that you eat. Do this for a few days so you can find the averages.
If you are currently maintaining your weight, you will want to drop your daily calories by 300-500. This will allow you to lose about 1lb per week. This is the best way to do it; if you lose 2lbs or more per week, you are probably going to be losing muscle along with fat (unless you are REALLY overweight, then you can drop weight faster in the beginning).