On rebound from the front wall, the other player must then retrieve the ball before the second bounce and return it back to the front wall. Each rally begins with a serve. The winner of the last rally serves the next and may choose from which side of the court service will begin. The server must alternate service boxes after winning a point within a rally. Points are earned by the server only.
Matches are usually five games.
For more details refer to the Squash 101 page in this website. In tennis, it's generally accepted that you string your racquet tighter for more control and looser for more power. No one seems to be certain if the same is true for racquetball racquets. For every particular racquet, string, and player combination there is an optimal string tension for maximum power. Typically that optimum tension falls nearer the bottom of manufacturer's recommended string tension, but not always.