best way is slowly and includes exercise. Walk every day. If you drink milk, switch to skim, if you drink soda, switch to water or diet soda. Make sure the bulk of your diet is healthy fruits and veggies, eat whole grains and really try and keep anything "white" out of your diet (other than milk or cheese!).
Depending on your sex, weight, and age there are a number of ways to do this. I would suggest going to myfitnesspal.com and finding out what your daily calorie intake should be for the desired weight loss.
I use the zig-zag feature that allows you to consume different calories each day (to keep metabolism up). As you lose weight, you'll need less calories to maintain weight, so you should update once you've lost 5 and 10 lbs.