Press-up
How to do it: Get down into a press-up position with your hands placed shoulder-width apart and back flat, so a straight line forms from your head to heels, via your glutes. Lower your body until your chest is an inch from the ground then explosively drive up by fully extending your arms. That's on rep.
Why: This move uses multiple muscle groups for maximum growth and strengthens your shoulder joints. Easily done as an exercise at home, this prepares you for progression to the more demanding shoulder exercises you'll face in a gym, like the incline bench press.