Weight is the main parameter
The weight of a squash racket is usually built into its name: 110, 115, 120, 125, 130 — these are grams. The lighter it is, the faster the hand and the more precise the short ball, but it does less of the work for you. The heavier it is, the more power and stability, but you need fitness and technique to keep control. A universal start for an adult is 120–125 g. If you like attack and covering lots of court, go lighter (110–115). If you play a power game, go heavier (130+).
Balance: toward the handle or toward the head
Handle-balance (head-light) — the racket feels light in the swing, forgives and gives control. Head-balance (head-heavy) — more mass in the hitting zone, so more power, but a slightly slower reaction. A neutral or head-light balance is more comfortable for beginners and amateurs.
Head shape
Teardrop — a large string surface and sweet spot, more power and forgiveness on off-centre hits. Closed (bridge) — a smaller area but higher accuracy and control, usually found on junior and control models.
For your level
Beginner — a forgiving, easy-to-handle racket (teardrop, 120–125 g, head-light). Confident amateur — an all-rounder to taste. Advanced — whatever brings out your style: a light head-light for a controller, a heavy one for a power player. And remember: half of a racket's feel comes from the strings and their tension — do not skimp on them.
Not sure? Come to a demo session at the S.Q. or «Theorem» courts: holding it in your hand and hitting a few balls is more useful than any description.