I gad a great coach and there were many gems in what he told me those long long years ago If I have to chose one each for batting bowling and fielding. . .
Best for Batting :
As the bowlers hand comes up for delivery look at it as if nothing else exists in the world and at the ball as it leaves the hand. If you watch the ball from the very beginning and do not take your eyes off it, the feet will move forward or back on their own.
This when I had already digested and was meticulously following the basic technique but was having trouble deciding on the length early enough.
Best for Bowling :
Keep your eyes completely focussed at the spot on which you want to pitch the ball and chances are you will hit it.
While Fielding (at cover/cover point) :
Walk in on light feet and watch the batsman intently and as he moves his hands and his feet your head will register it and tell you where the ball is going.
He was spot on. It worked.