Here are the five keys to building a solid backhand:
1. Well timed split step.
2. Superb Unit Turn - Watch how Novak's right arm is almost horizontal at the furthest point of his take back.
3. Tip of the racket gets below the hand by quite a bit on the drop: A quick note here, a common problem is players who 'tip' the shoulder, or drop the hand down, leaving the racket tip still above the hand.
4. The 3 H system: 'H'ip brings the 'H'ands to the ball while the 'H'ead stays still.
5. Full extension, have a look at how far extended Novaks left hand is after contact.
6. Absorb the energy with the shoulders, and clear the elbow.
You will notice how Novak gets his playing hand elbow around as he reverses his shoulders, (front shoulder becomes the back shoulder) and its ends up pointing at the back corner.