Fruit and vegetables. Make friends with apples, bananas, celery sticks with peanut butter (the apples and peanut butter are good too and peanut butter and bananas sandwiches for breakfast are great!). Make sure what you eat is nutritiously packed so it will help you stay full, longer -- start with fresh food; not packaged, fast food or snack foods. Go to a large grocery store and walk every aisle; mine done with my pedometer was half a mile! Make a game of it, everywhere you can. If you have to wait for someone at an appointment or something and you are in the car, do incline pushups against the car, play balancing games on the curb, use the curb for a "step", etc.

Find a site you like (I love The World's Healthiest Foods) and see what you can learn about nutrition and simple cooking, etc.