Counting points played in good faith. All points played in good faith stand. For example, if after losing a point, a player discovers that the net was four inches too high, the point stands. If a point is played from the wrong court, there is no replay. Corrective action may be taken only after a point has been completed.
Some players confuse warm up and practice.
A player should make a special effort to hit his shots directly to his opponent. Take all your warm-up serves before the first serve of the match. Courtesy dictates that you not practice your service return when your opponent practices his serve. A player calls all shots landing on, or aimed at, his side of the net. Opponent gets benefit of doubt.