Warm up before starting your workout to get the blood flowing and avoid injury.

Do the following warmup cycle:
 - Hang on the pull-up bar for 10–15 seconds.
 - Get in the push-up position and hold it for 10–15 seconds.
 - Drop your hips to the ground and stretch your abs.
 - Lift your hips to the sky and stretch your hamstrings and your back.
 - Stand up, squat slowly, and sit at the bottom for 10–15 seconds.
 - Do a burpee and a few jumping jacks.
 - Now go back to the bar and do one pull-up.
 - Drop down and do a push-up, then do a slow dive-bomber push-up.
 - Stand up and do a slow, full-range-of-motion squat followed by a burpee, then five jumping jacks.

Repeat the cycle, doing two repetitions of each exercise and ten jumping jacks.

Do the cycle with three repetitions of each exercise and 15 jumping jacks.

Continue increasing repetitions until you get to 5 of each exercise and 25 jumping jacks.
That is a solid warm-up; the blood is flowing.

If your workout for the day is focused on a specific movement, do that movement with some light weights.
For instance, if you are doing deadlifts, do some deadlifts with light weights through the complete range of motion to get your body warm and strengthen your muscle memory of the movements.