Tennis players should change ends of the court to ensure that both players have to deal with the weather conditions on either end of the court, such as the sun or wind. The pros even do it so they both have to deal with the same loud, annoying person in the crowd.

Each time the number of games played in a set adds up to an odd number, the players change ends of the court. For example, after the first game, the cumulative number of games played is one, so the players change ends. After the next game, the number of games totals up to two, so the players stay put. Then after the next game (now a total of three games), the players again do the old switcheroo.

If a set ends in an even number of games (say, 6-4), you don't change ends until after the first game of the next set.