1) You must eat frequently. Eat 5 to 7 times a day but the meals should be smaller than that half of a Domino's Pizza you are currently eating for lunch. Stay away from chips, beer, and other emtpy sources of carb-calories. High quality protiens (chicken, turkey, salmon, etc) and good complex carbohydrates (apples, broccoli, and the like).
2) Drink more water. When you think you've had enough water drink some more.
3) Exercise. Get off your arse and do it. Five to six days a week preferably first thing in the morning. Alternate resistance & cardio. You can get a good workout done in less than an hour. Look for more information here:
Body For Life
4) Get a good night's sleep. 8 hours...maybe 9.
5) In 10 to 12 weeks enjoy the new you!