That's a good attitude, I hope you really stick with it. I can't emphasize cleaning up your diet enough.. if you go to the main "Diet & Nutrition" forum page, you will notice that there are a couple threads at the very top that are "stickies" -- read those and understand them. I believe there is a grocery list of good food choices: carbs, proteins, fats.. check it out, you want to make sure you get enough of each macronutrient.
Emma said to eat less calories than you burn, but make sure you are eating enough. Breaking your eating into 5 or 6 smaller meals will keep your body going all day, and your metabolism higher. Keep in mind, when you are eating "clean," you are getting less calories than if you were eating the same number of meals at Burger King, so definately make sure you are eating enough. And don't think "fats" are bad.. you need good fats to lose weight.
Keep us posted, and don't be afraid to ask questions!