Set-up: Find a bench or other suitable object roughly one to two feet high, and clear a space of about 6 feet. Plant your working foot roughly several feet in front of the bench, and place the top of your stabilizing foot flat on the bench.
Lift: Bracing through your core, descend to a point just before your knee touches the floor. Quickly reverse the motion.
Emphasis: Brace through your core at all times. Keep a neutral spine throughout the duration of the movement. The knee of the working, forward leg should be in-line with the toe of the working foot.
Repetitions: Perform all prescribed reps on one side, then on the other. This counts as one set.
Assists: If stability cannot be maintained, try setting up using the wall or another object for support. Progress by using less and less support until none is used at all.