The diet for a sedentary person is different from that of an active person. Eat three regular meals per day. No snacks, not even when you are watching TV or working on a computer. No sodas, no fruit juices. Order only water in a restaurant for your drink.
Many people order a soda or a dessert in a restaurant under peer pressure.
Remember your metabolism has not changed because you are in a restaurant. No buffet, no fast food. Try to eat at home as much as possible. Try to prepare your meal yourself, at least over the weekends. Get involved in your food.