You want to work your muscles and then you want to stretch 'em. If you have been doing dumbbell front raises, or front rowing, you have been working your deltoids -- The muscle on the top of the arms that is so fun to show off by wearing tank tops. You want to keep the muscle flexible by doing this stretch for your deltoids.
Hold for 10 to 15 seconds
Switch arms to stretch your left deltoid. Repeat the stretch twice on each arm.