From a seated position, bring yourself off the seat a few inches and hold (that's the "hover squat"--you can also start in the upright position and lower yourself until you are a few inches over a seat). Then do shallow pulses, staying near the bottom end of the squat, for a count of eight (each count being 1 pulse up and down), then either sit, or stand upright and repeat (it's safer to do this from the standing position when using heavier weights, because you can jar your spine otherwise).