Don’t think about “serving the balls” but “starting the rally with the toughest shot you can play”.
The best first shot really depends on your opponent, but the minimum you should be aiming for is to stop them hitting a winner and ideally force them to play a weak return.
One small problem club players face in this regard is what the professionals do.
Watching on a screen never really shows how difficult their serves are. How often have you seen aces in squash. *Even after all these years in squash, I’m never sure if that’s the correct word for a winning serve!*
You also see many professionals hit fantastic nicks from serves and this can give the false impression that professionals just hit the ball without much thought to start the rally. They don’t.
I can guarantee that if you were to face their serves you would find them quite difficult to return well.
Almost all good serves hit the side wall before the returner has a chance to hit it.
A ball coming off the side wall is one of the hardest for club players to hit straight, that’s why so many returns for difficult serves are hit crosscourt.
When you serve make it as difficult as possible for your opponent to hit good return.
In fact, when playing practice matches, make sure you go for some high serves, even if you hit them out – it’s worth the practice.