To properly perform a chin up:
1. Grip the bar. Tighten lats, core and back stabilizers.
2. Pull using back and biceps to the top of the bar.
3. In a controlled manner, extend shoulders to starting
position.
Jeremiah's Expert Training Tip:
To increase total number of pull-ups you can do at one time, train in clusters; i.e. 5 rounds of 3x(2 pull-ups w/15s rest in between each group of 2). You
will be able to do more total pull-ups vs. doing straight sets, and your pull-up
capacity will increase.