Your feet stay on the floor, no jumping, and you always have a stabilizing arm on a chair, wall, door frame, whatever's necessary, in a super-plie. I'll try to describe:
First, here's a picture of a simple plie squat in second position. You DO NOT have to get this low, your feet only need to be about 12 inches apart to begin with, and you do not have to use dumbbells. Use one of your hands to steady yourself on a wall or something stable, and when you squat, make sure your knees go out over your toes.
Step one: Again, your feet are 12 inches apart, and you bring yourself into the squat to the point where you can't go down any further, but not to pain.
Step two: Still down in the squat, you lift your heels so that you're on your toes, but still squatting.
Step three: Lift your body back up to standing, still on your toes, don't lock your knees.
Step four: Go back down in the squat, still on your toes.
Step five: put the heels back to the floor
Step six: Raise yourself back to standing.
Sounds complex, it's not, I swear. Once you get the basic movement, squat down, heels up, body up, body back down, heels down, stand up. I do it to music that's about medium tempo.
I also do the same squat with my feet in all the foot positions below, to fatigue all the muscles, and do ten reps in each position. Pay no attention to the arm positions, just look at how the feet are positioned. And I was, by the way, doing this when I weighed 300 pounds, and with a seriously buggered-up knee. Just keep stability in mind at all times, and START SLOW. This works every muscle and tendon in your legs, and if you keep your body posture ballet straight and focused, will do some gentle work on your core, as well.
