I have yet to come across a better overall summary of things to think and work on to improve your squash game than the 27 tips found here:
The Squash Site
This is a great page to bookmark. The tips were penned by Sakhi Khan, head coach at Colby College, of the sainted Khan squash dynasty, now in its fourth generation. I refer to this list regularly, sometimes ruefully wondering why on earth I don’t do this tactic better, and sometimes just to remind myself of the tactics enumerated so I can go out and practice them next time I’m on court.
If you are a new player, the list will seem a bit overwhelming, but get a good pro to give you some lessons and keep plugging away at it. If you are an experienced player, some of the tips will seem too easy, but no matter what your skill some of the tips should be reviewed again and again. For instance, Khan’s discussion of the drop shot is worth a re-look from time to time. Like right now.
If you are a squash player and can execute these tactics and learn these tips, then you got game. This is your bible...