Breaking the yo-yo dieting cycle is difficult because consistency is everything! Here's some tips gleaned from success stories of those who are no longer "yoyo-ing". You'll never get control of your weight without exercising. Join a gym and take an aerobics class twice a week. A surge in your energy level will be the first benefit. Weight loss should quickly follow. Strength training added-on to your plan will help sculpt your muscles and change your body shape.
You might have a few lapses though. Christmas binges for example, could lead to weight gain. You should start weighing and measuring your food. Once you decide to recommit to your exercise / aerobics / strength training / measuring portions strategy, and your weight loss will become permanent. For those no longer on the weight-loss yo-yo, those are the pieces to the puzzle.
For those doing Weight Watchers, simple replace the "measuring portions" piece with a "counting points" piece. Either way, you should have the puzzle solved!