Which service box do I serve from?

Under Rule 5:

• The player who wins the spin of a racket serves first.
• At the start of each game, and every time the serve changes hands ("hand out"), the server chooses which box to serve from.
• While you keep winning rallies, you must serve from alternate boxes.
• After a let, serve again from the same box.
• If you go to the wrong box, the marker should tell you. If it goes unnoticed, the result of the rally stands, and if you won it you serve next from the other box.
• Do not serve until the score has been called, and not before the receiver is ready. If the receiver is not ready and does not try to return, it is a let, but a serve that is a fault still loses the rally.