Pull-ups are performed by the assistance of a sturdy bar that is positioned roughly arms length above the floor.

To perform a pull-up (also known as a chin-up) you grasp the bar with both hands spaced roughly shoulder width apart. I have seen variations on the grip that range from palms facing out away from you, palms facing toward you, or one hand facing either direction. The most common 'right' way I see defined is with palms away from you, each position will train slightly different muscle sets, so experiment for what is best for your workout or use a combination or alternating grip.

Gripping the bar use your bicep muscles to lift your body up until your chin is able to touch the bar (chin-up), then slowly lower back to the start position.

If your bar is not far enough off the floor you can bend your legs with your knees up in front of you or bent back behind you.