first, remember that this is a lifelong process of changing how you live, and only part of that is eating...this means that you should just do your best to be healthy, eat right (avoid fad diets) and slowly increase your activity level at a rate that works for you. Try informational websites like www.fitday.com which will help you determine how much you take in and expend in calories everyday. If you average about 500 calories a day diffence in the amount you eat vs. the amount you expend, you will lose a pound a week. And trimming 500 calories a day is pretty easy.
good luck and advice
Take it slow and do it for life! Good luck! :)