The players usually spin a racket to decide who commences serving at the start of the match and this player starts the first rally by electing to serve from either the left or right service box. For a legal serve, at least part of one of the server's feet must be in that box and, after being struck by the racket, the ball must strike the front wall above the service line and below the out line and land in the opposite quarter court, unless volleyed by the receiver.
The players then take turns hitting the ball against the front wall (referred to as 'rallying'). The ball may be volleyed (hit whilst still in the air) or after its first bounce and before the second. To be considered 'good', the ball must reach the front wall below the 'out' line and above the 'board' or 'tin', before touching the floor. A ball landing on either the out line or the line above the tin, contrary to tennis, is considered to be out. The ball may also be struck against any of the other three walls before reaching the front wall. Shots that are first played off the side or back walls are referred to as 'boasts' or 'angles'.
The rally continues until a player is unable to return his or her opponent's shot or makes a mistake (e.g. hits the ball 'out', or hits it after its second bounce, or onto the floor, 'board' or 'tin'), or a 'let' or 'stroke' is awarded by the referee for interference (see below).
In the 'traditional' British scoring system (as adopted in 1926), a point is scored only by the server (when the receiver is unable to return the ball to the front wall before it has bounced twice). When the receiver wins the rally, they are awarded only the right to serve.
Games are usually played to 9 points (alternatively, the receiver may opt to call 'set two' and play to 10 when the score first reaches 8-8). Competition matches are usually played to 'best-of-five' (ie. first player to win 3 games wins the match).
Alternatively, in the point-a-rally scoring system (often referred to as PARS or 'American' scoring), points are scored by the winner of each rally, whether or not they have served. Traditionally, PARS scoring was up to 15 points (or the receiver calls 15 or 17 when the game reaches 14 all). However, in 2004, the PARS scoring was reduced to 11 for the professional game (if the game reaches 10 all, a player must win by two clear points). PARS is now used on the men's Professional Tour.
In the 'international' game, club, doubles and recreational matches are usually played using the traditional 'British' scoring system. Scoring systems and rules can be adapted subtly to accommodate shorter game time (e.g. games played to 7 points, best-of-three games) or multiple players (e.g. a form of squash called three-quarter court, where one service box is blocked out and excess players wait in that area while two players play a single point in the remaining area of the court). The 'British' scoring is generally used for USSRA (United States Squash Racquets Association) matches.