Start in a plank position with your hands on your coffee table or the sturdy arm of the couch. If you have neither, just do push-ups on the floor, resting your knees on the ground if you need to.
Pull your abs in and squeeze your glutes to stabilize your core. Inhale and bend your elbows to lower your head; exhale, pulling your navel to the spine, and straighten your arms, returning to plank.
Too easy? Flip your body around so your feet are on the coffee table and do push-ups this way.