Push Ups
"Place your hands approximately shoulder width apart. Hold your body perfectly straight and exhale as you push your body up until your arms are straight. Pause. Inhale as you lower your body to the floor, allowing only your chest to touch. Your stomach should still be an inch or two off of the floor when you touch with your chest, because your toes lift the body up a bit." (Arnold: The Education of a Bodybuilder p. 163)
Modification:
"If you are new at this exercise and do not have the strength to perform it, you can either bend your legs at the knees to take off resistance or perform the exercise against the wall instead of the floor.
"For the most advanced lifters, you can place your feet at a high surface such as a bench in order to increase the resistance and to target the upper chest more." (Bodybuilding.com 2012)
Modification:
"If you are new at this exercise and do not have the strength to perform it, you can either bend your legs at the knees to take off resistance or perform the exercise against the wall instead of the floor.
"For the most advanced lifters, you can place your feet at a high surface such as a bench in order to increase the resistance and to target the upper chest more." (Bodybuilding.com 2012)