You need to realize dieting isn't the best solution.
First, find your metabolic rate. If you see a doctor, they can help you find this. Counting calories will not be effective if you don't know how many calories your body burns.
Second, control portion sizes. You can eat and drink any food or beverage, but the portion sizes are what need to change. Can't eat an entire pizza and expect to lose weight the good way, after all.
Drink lots of water and limit the amount of "empty-calorie" beverages (sodas and energy drinks have calories but no nutritious value). Drinking water actually will cause your stomach to stay full longer so your body doesn't send the signal "feed me!" to the brain.
Eating 6 small meals every 2-4 hours is the best way. Breakfast, Snack, Lunch, Snack, Dinner, Snack. The snacks should be smaller than the actual meals.
Exercise is important as well, but you should find your own pace for exercise. Some people aren't made for running marathons straight off the couch, after all.
Check out this website: SparkPeople.com it's got tons of great tips and success stories. It's free, and you can pace yourself.