For the beginner: With your knees on the ground and hands a shoulder-width apart on the ground, lower yourself as far as possible and push yourself back up.
You want your shoulders, hips and knees to be in a straight line, with your shoulders directly over your hands.
Make sure your elbows point outward to 45 degrees (as opposed to 90 degrees outward), when you lower yourself to the ground.
You can modify this to an inclined pushup if needed.
Helpful tips and Tricks
If this is too difficult, start off with your hands on an elevated surface, such as the couch, chair, fireplace, table or even a window sill.