Place hands directly below armpits, raise up on to toes and keep the back as flat as possible. There should be a solid, diagonal line from the ankle to the neck.
Keep the body in line as the elbows bend and the chest is lowered towards the ground. The abs must remain tight to keep the lower back from sagging. Keep the palms firmly planted to the ground and the elbows directly above the wrists.
If a good posture is impossible to keep with the toes on the ground, lower the knees to the ground and complete push ups from this position.