Start by making changes you can LIVE with for the rest of your life. Too often people go from eating fast food everyday to eating 800, 1,000 or even 1,200 cals. per day. This is unsustainable long term.
Start making some "informed" decisions about weight/nutrition and how they effect one another. Add a balanced exercise plan (again, don't go from couch to working out 7 days a week...this is a recipe for inevitable failure). Perhaps start with 20 mins cardio 3 day/week. Work up slowly, maintaining for at least 2 weeks your current workout schedule.
There is much advise you can get right here from just reading the many threads here at 3FC's calorie counting section with all types of info to help you figure out where you need to be.
If you want to weight off, and you don't want to lose muscle, expect to lose safely between 1-3 lbs/week. A safe starting caloric range for most is between 1500-1600 cals/day.
Hope this helps.