Place the loaded barbell on your back (resting across your traps and shoulders) and spread your feet a bit less than your shoulder width. This is your starting position.
While keeping your back straight and butt out, squat down all the way until your legs are bent at a 90-degree angle (you can go deeper if you are confident that your can easily push back up without failing). Then, push back up with your legs as strong as you can and get back into the starting position. Don't completely lock-out your knees because you should always keep tension in your legs for maximum movement efficiency.
Repeat the entire movement for the desired or prescribed number of repetitions.
Perform this exercise in a smooth and fluid motion
Your head should be up as if you are looking into the horizon
Don't lock out your legs (knees) 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.
This is a great exercise for the legs. It's a modification on the regular (stance) squat which means it's a bit more difficult to execute. It will do wonders for your quads and hamstrings too. The key with this movement is not to rush it. Give it a good slow squeeze as you go down.