Set up on the machine by getting under the loaded bar with your feet close together and a bit forward so that you are in effect leaning into the Smith bar. This is your starting position.
Unhook the safety mechanism and squat down all the way until your legs are bent past a 90-degree angle. Then, push hard with your legs and get back up to the starting position but don't lock out your knees completely; you should always keep tension in your legs for maximum movement efficiency.
Finally, repeat entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Setting up properly in terms of foot positioning is important, so do a few practice repetitions with the empty bar to gauge where you should be placing your feet so that your are neither leaning in too much nor too deep under the bar
Don't extended and lock out your legs completely on the upward portion of the movement
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
To increase the level of difficulty, slow down the movement or increase the weight.