It is the best exercise to get your beach body. And if you aren't going for your beach body, well you are just crazy! Push-ups work every muscle from your shoulders down to your back.
Start in a prone situation on your toes and your hands underneath your shoulder. Bring yourself up to be flat as a board and then bring yourself down by bending your elbows. Keep yourself flat as a board and your abdominals tight throughout as your push up and down repeatedly.