How is the score kept and announced?

• Games: love, 15, 30, 40, game. At 40-40 it's deuce, and you must win two points in a row from deuce (ITF Rule 5a). "Zero, one, two, three" or hand signals are also fine.
• Announcing: the server announces the game score before the first point of each game and the point score before every point (Code 31).
• Sets: at 6-all, play a 7-point tiebreak (first to 7, win by 2); it's mandatory in all sets of sanctioned tournaments except pro sets (USTA Reg. I.E.1.a). The player due to serve serves the first point, then each side serves two points in a row. Change ends every 6 points (Rule 5b; USTA Comment 5.3).
• Match tiebreak: many events play a 10-point match tiebreak (first to 10, win by 2) instead of a third set. The entry form must say so (Reg. I.E.1.b).
• Score disputes: count all points and games you agree on and replay only the disputed ones (Code 32).

A point played in good faith stands, even if a mistake (like serving from the wrong side) is found afterward (Code 2).