Set-up: Find a pull-up bar and assume an underhand shoulder width grip.
Lift: Bracing through your core, lift yourself up until your chin is over the bar, trying to get as high as possible. Cue yourself to pull your chest to the bar to ensure full height. Descend all the way to full extension as this will engage more of the shoulder stabilizers and muscle mass of the back - this will help in maintaining health in the shoulder girdle.
Emphasis: Do not swing your body up to the bar. It will change the movement pattern and should functionally be considered a different exercise. While useful in other contexts - swing and momentum are inappropriate here.
Optional weighting: A weight belt will allow for external loading to make the exercise more difficult.
Assists: A machine appartus may be used to provide assistance and make the exercise easier. Alternatively a partner may provide assistance, or placing your feet inside elastic bands wrapped around the pullup bar.