A few tips that have helped me!

First off you need to have some sort of food journal whether it be the weight watchers one or a piece of paper and pin. Keep track of every thing you put in your mouth even water. This will let you know exactly what you are putting in your body! I would sometimes find myself thinking I have done this for a while now I can tally this in my mind. I often end up making catastrophic errors and it always shows on the scale when I don't journal my food intake. Second measure your portions. Sometimes I eyeball it and usually find out I ate a extra 1/2 portion. The portions tend to creep up on you again.
Second get moving you burn twice as many calories standing as you do sitting. So if you don't have a regular routine just make small goals. I don't recommend going out and working out four 2 to 4 hours your first day exercising. You wont be able to maintain that for long and the minute you don't follow through with that you will feel failure and want to give up. So make small goals that you can easily obtain and help build your confidence in yourself. Then you can bump those goals up a notch slowly. Never set your self up to fail. By saying in going to lose 4 pounds this week if you lose 3.5 you did not reach your goal even though that's a great number will still make you feel less happy with your self but if you say I'm going to walk 15 min every day for 5 days and then lose 3.5 you will be happy. Also never reward yourself with food. You are changing your lifestyle so there is no reason not to fit in a favorite food every once in a while. All you need to do is plan.
Planning is the key to success in all aspects of life. Plan a certain time you are going to work out. plan meals out plan ahead and have guilt free snacks in your car for when you are starving and on the road and passing a McDonald's. Plan what you are going to eat before you get to the restaurant to meet a friend that way you wont be tempted to just order the bacon burger with fries. Many restaurants have nutrition facts on there websites visit there before you leave the house.
Find ways to make your favorite food healthier like using fat free cheese or fat free cream of chicken soup.