Building up a good solid exercise base is key. You can lose weight with a diet, but getting your body moving is the biggest secret of all! And the more you move, the more weight you'll lose, the better you'll feel and the more sure of your success you will be!
It doesn't matter what you start with, just START. Walk, bike, do jumping jacks, get in the pool . . find something you LOVE. And keep on doing it!