Ask The Master: What decisions do I make before a shot n how long must it take?
You should make ALL of your strategic (why), tactical (what), and execution (how) decisions before you bend down into your stance. If you're down and have doubts or a better idea of what to do or how to play the shot, stand up, chalk up, and start your planning process over. Your body is set up for what you originally had in mind. If you change your mind, you have to change your body.
The decision process takes as long as it takes. Don't shoot until you are clear about:
(Why) you're going with this plan
(What) is your shot
(How) exactly will you shoot it.
Sometimes there are many possibilities that must be weighed. Take a lap of the table. See the shot. Feel the shot. Believe the shot. Shoot the shot. Take your time.
I've written two articles that address these concerns: Don't Bend Over Without a Plan and A Routine Investigation. Just send me an email requesting these articles and I'll get them right out to you.