Rules of Play

Arrive at the assigned table punctually for the start of a game. Your late arrival is discourteous to your opponent, and could cause the tournament to run late.
Do not talk or rattle tiles during pre-game announcements.
It is not acceptable to use mobile phones (receiving or sending) in the playing area while any game is still in progress. (Permission to receive emergency calls may be obtained from the TD.)
It is expected that more experienced players will help newer players if they are unsure of procedures and rules, especially in relation to scoring, challenge and the use of clocks. For example, reminding a less experienced player who forgets to press the clock.
It is not acceptable during a game to ask your opponent if a word is allowable, (yours or theirs), or to ask what a word means.
Play your tiles the right way up, with the number at the bottom (e.g. N, I, O). Place tiles properly on the squares.
Respect the equipment. Do not mark tiles or boards with pen/pencil. It is advised not to bring cups or glasses to the playing tables.
Place the tile bag within comfortable reach of both players.
Keep any comments, unnecessary conversation or other noises to a minimum during a game, to reduce distractions not only to your opponent, but also to surrounding players.
Avoid saying aloud the word that you are playing so that your opponent cannot be misled or confused by a mispronunciation of the word played.
Avoid “stream of consciousness” talk about your decision-making.
Especially refrain from moaning or commenting during the game about your tiles or your luck; that can also be construed as a ruse that can mislead your opponent into making a play which advantages you.
You may warn your opponent not to draw tiles while you are considering whether to challenge (see Rules 6.1 and 10.1), but be aware that you are thus preventing your opponent from seeing their new tiles and legitimately thinking about their next move. Therefore, unless you have any doubt about a move, it is courteous to accept a move immediately, by writing the opponent's score.
The clock is neutralised during a challenge, or to resolve a score discrepancy (Rule 3.3), or when the TD is called. When the matter has been resolved, the person whose turn is over should restart the opponent's clock. That said, either player, of course, may restart the clock.
Whilst it is advisable to confirm cumulative scores at intervals during the game, it should not be over-frequent, because it can break the opponent's train of thought. This should be done on your own time (Rule 6.3).
Absence from the playing room has moved to Rule 6.6 (Jan 2020)
It is not obligatory to announce the number of tiles left in the bag when you count or draw tiles, or to indicate to the opponent when the bag is empty. (It may be polite to do so, but the opponent shouldn't rely on it, in case you are mistaken.)
When a game is over you may want to discuss aspects of that game with your opponent or with others before you clear the board. However, after handing your result sheet in, your first concern should be for nearby players who are still playing. It is unacceptable to disrupt their game with your conversation.
At the end of each game, clear the table of debris, challenge slips, rubbish, own equipment, so that it is ready for the next users. Please also return any equipment that you have moved.
If observing a game, leave a comfortable distance around the players, stay absolutely silent, make absolutely no indication of your opinion of a player's rack or the board, and do not look up words. Call the TD if anyone is disturbing your game. The TD may modify or put a halt to observation if indicated. (Rule 12.4)
Refrain from wearing strong perfume or after-shave, as many people react adversely
All players are requested to maintain a reasonable level of personal hygiene to minimise mouth and body odours, and to maintain a clean, undistracting appearance.

Tournament Etiquette Guide