Take on a gym membership. I have one(despite my injury), and work out whichever body area I want to target. There are some great fitness trainers, and there are a lot of options as far as cardio, dance or weight classes.
Wanting to get in shape is a nice concept, but like every human being out there, the idea of working out tends to go away quickly once you realize how much work it really involves. Getting yourself a gym membership will allow you to meet some new people, make a work out buddy and guilt yourself into going since you pay for it.
Good for you for getting yourself into shape.