The squash thinking is referring to how or what to think prior to a match and during a match.
It's a question that perhaps is quite personal. I've been coached by some players, and of course listened to the bar talk after some great matches. The results of which follow:
During a Match
The advice I was given about thinking on court was constantly thinking about the next shot. For example, during a match, watch the opponent. Start to think what shot will they play, and then what shot you will play to counter/attack it. This thinking is easier when you play such a good shot as to limit what they can do.
When they hit the ball, think about two things on the way to the next shot. Early racket preparation and what shot are you going to play?
You are then 100% clear on your shot, and if you get good at this thinking, a couple of things can happen. Firstly you can hit your shot with better quality, you've longer to prepare. Next, with practice, you can start to disguise your shot.
Other advice I have received is to keep your mind open, and approach the ball thinking of 2 or 3 shots.
Any more advice, please email it in.