The overhead squat builds on the mechanics found in the air squat. Only this time, the load (generally a barbell) is kept above the head, balancing at the center of mass.
The overhead squat is amazing at developing core stability. It also has no peer in weightlifting to test flexibility. For these two reasons, as well as the lack of knowledge from both trainers and trainees on this relatively simple movement, the overhead squat is endangered.
Let’s dive into the set-up and execution of this almost extinct lift.
Set-Up
When learning this movement, use a broomstick or something else that weighs less than 5-lbs. Once you find your object, stand with your feet shoulder-width apart.

Next, grip the barbell so that your hands are wide. Your flexibility and preference will ultimately determine where exactly you will place your hands, but the underlying rule is that you should be able to perform a pass-through.

Finally, extend your arms overhead while rotating your armpits forward. Locking your elbows out and rotating the shoulders back, externally rotates your joints and creates stability for the barbell. Bent elbows and/or internally-rotated shoulders will not support any significant load overhead.
Execution
An athlete should not attempt to overhead squat without first mastering the air squat. The danger present with a load overhead should not entertained with the athlete unfamiliar with proper squatting.

The difference in the overhead squat lies in keeping the barbell over the middle of the foot. A 1/2-inch shift in the barbell moving forward or backward will send the load tumbling to the ground.

When practicing this movement with a light load, ensure the barbell stays in a straight line, directly over the middle of the foot.
Happy squatting, friends.
Tyler
WOD
3 Sets:
1:00 Max Reps Air Squats
1:00 Max Reps Chair Dips
1:00 Max Reps Plate Hops/Line Hops
1:00 Max Reps Burpees
1:00 Rest
*Images used from here.