Hands should be positioned slightly outside shoulder-width, at chest level.
Keep your abs tight; it should look like you’re doing a plank while moving up and down.
Bring your elbows down & back (not out to the side – see video), to lower your body towards the floor. Drive yourself up by forcing your hands into the floor hard.
TIP: These can be performed on knees if full push ups are too difficult for you right now.