What's the Best or Correct Technique?

[Enga]

Watching the swing and the ball are most important I think. You can get clues by watching them before they swing but it's not a guarantee, so if you commit too much before they hit the ball you might be going in the wrong direction.

 

[Kevo]

Do you think Djokovic is strictly watching the other guy swing at the ball and right at that moment (ball contacting) he's hopping up both feet? He's got to be watching his opponent's swinging/contacting the ball to catch that split second to synch up w. his own movement (the hopping), right?

He's not "strictly" watching the ball, but he's definitely watching the ball. After so much training over a long time your brain handles a lot of non-conscious processing for you. The split step is just one piece of the overall reaction/anticipation puzzle, but it's super important. Most people develop the split step quite early and it gets trained every time you hit so it becomes second nature. If you don't have a good split step then you should certainly work on that before moving to anything else related to improving your reaction time during rallies. It's fundamental to good court movement and if you don't have it right you are at least 1 step behind where you could be.