The problems: Keeping your torso vertical, flaring your elbows, not dropping low enough.
The first two mistakes are very tough on your shoulders. The third one is a cheat that limits the effectiveness of the move.
How to fix it: A correctly executed dip is an incredibly effective upper-body builder that nails your triceps and works your chest. Do it wrong and you’re in for a world of hurt — not to mention looking and feeling awkward as hell.
• Grab the handles of a dip station and lift yourself so that your arms are straight. Cross your ankles behind you. This is your starting position.
• Keeping your forearms vertical and elbows tucked (not flared), allow your torso to lean forward as you lower your body until your upper arms dip just below parallel to the floor.
• Reverse the movement to return to the starting position.
Make it easier: Strap an exercise band between the bars and place a knee or two in the loop as you perform the exercise. The band will help lift you out of the low position.