Assume a push up position, arms straight, hands directly underneath the shoulders, feet together. Engage your core by assuming a Posterior Pelvic Tilt (Tuck your tailbone, eliminate any arch in your back). Squeeze your glutes, there should be a straight line from your head to your heels.
Generate total body tension, gripping the floor, squeezing your armpits.
Bend your elbows, and as your descend do no allow them to drift backward, your shoulders should move ahead of your hands. Keep the elbow tucked into your sides, and lower your chest to the floor. Maintain a strong posture throughout, do not let your back arch or hips sag.
Pause at the bottom, then drive into the floor, screwing your hands outwars to help create tension and and push yourself up, exhaling on the way. Fully extend your elbows, squeeze the triceps and protract the scapula as much as possible. Squeeze at the top, and repeat for repetitions.