PREPARATION
1.Kneel on the floor. Lean forward
  and place your hands on the
  floor, well forward of your
  body and out to either side,
  palms flat.

2.Straighten your legs, raising
  your knees off the floor and
  pushing your body forward, so
  that your shoulders are just in
  front of your hands.

3.Make sure that your back is flat
  and your head is in line with
  your spine. Breathe out.

EXERCISE
1.Breathe in as you lower your
  chest to the floor. Keep your
  elbows out away from your body
  so that you feel a good stretch
  across your chest.

2.Hold briefly, then breathe out
  as you push up, raising your
  body away from the floor. Do not
  lock your elbows.

Do not rest between repetitions.

MAINLY FOR: Anterior deltoids
            Pectorals
            Triceps

For press ups which work the
arms more and the chest less, see
the exercise "Press Up, Narrow".