adapted from Smogon's thing
Instead of forever reiterating all the basic rules, you only have to forever reiterate a link to this post. How convenient!
Ideas thread (post or up-vote ideas here)
The stuff in this post is not finalized. Please tell me if you think anything should be changed.
The tournament idea and tournament host have the final say in everything and are allowed to make any part of this post not apply to their tournament. If you want to play in a tournament, then please read that tournament's thread as well as this one.
Signing up for a tournament
Signing up for a tournament is a commitment to playing. Tournament players are expected to check the tournament thread preferably every 1 to 2 days and at least once per week until they're eliminated from the tournament. If you cannot do this, then do not sign up.
To sign up for a tournament, all you have to do is post an answer before signups close. Your answer should include your Showdown! username and time zone, like this.
If the host isn't really sure about what to ban and is letting you vote on bans when signing up, then your signup answer should look something like this.
ban Maractus and cleanse tag, allow double team
(if you don't mention something in your vote or tell the host to ignore your vote, then your answer will be treated as an "allow" vote) A few tournaments have limits on players. But if you see a tournament that has already reached its signup limit, then you can still sign up as a substitute and hope you can substitute someone who drops out.
Scheduling tournament battles
When you find out who your opponent is (or in non-bracket tournaments, as soon as the tournament starts), you should immediately try to schedule a battle. The best way to do this is commenting on the answer that the opponent used to sign up. Compared to other kinds of communication (like wall posts), comments can be posted by any user (wall posts require points) and are difficult to delete. More importantly, the tournament host can more easily read your comments and see that you are trying to finish your battles in time. The ideal scheduling conversation should go something like this.
Player 1 tells player 2 a bunch of available times.
Player 2 picks exactly one of those times and also gives a list of his/her/its other available times in case there's an emergency.
Player 1 confirms that he/she/it has seen player 2's comment and can play at that time.
If your opponent tries to contact you, and you don't respond for a whole week, then you will be disqualified. If two players are matched up, and neither makes any attempt to contact each other for a whole week, then one will be randomly disqualified.
If you miss a scheduled time, then you should tell your opponent as soon as possible, ideally a few hours before the scheduled time, and try to schedule another battle. If your opponent misses it (and doesn't do what the previous sentence says), then you should wait about 15 minutes. If he/she/it still doesn't show up and doesn't tell you, within 12 hours, why he/she/it didn't show up, then you can ask the host to disqualify him/her/it.
Playing in tournament battles
Winning every battle in every tournament is kind of difficult. These resources can hopefully make it easier.
Pokemon Database Battling Guides
Smogon's competitive battling FAQ
Smogon's resources for beginners
Smogon Strategy Dex
Basic rules that might not be forever reiterated (as mentioned before, the tournament idea can freely change these)
Smogon (latest generation) OU clauses
Changes to bans (OU bans or bans in the tournament) start applying when a new round starts.
Single elimination best of one brackets
Battles are to be held on the Pokemon DB Showdown! server.
Save replays and show them to the host. You can make them private if you don't want anyone else to see them.
Players can change teams between battles.
If someone disconnects during a battle, then the opponent can take the win or redo the battle.
Rules must absorb H+ ions. :P
Doing these things usually leads to immediate disqualification. Doing them multiple times might lead to worse stuff.
During battles, spectators can't give advice, and players can't ask for it. In best-of-3's and best-of-5's and stuff like that, this applies between battles within a round. Clarification about what counts as advice:
Requesting that someone do a calculation for you to save time: Allowed
Doing a calculation that was requested by the player: Allowed.
Linking a RMT, paste, or public replay of the opponent's team if requested by the player: Allowed.
Pointing out that their timer is low: Allowed.
Asking or answering questions about a mechanic: Allowed.
Doing any calculation that was not requested by the player: Not Allowed.
Speculation of any kind (like "this Landorus has to be scarf"): Not Allowed.
Linking the player a private replay of the opponent's team: Not Allowed.
Suggesting decisions of any kind (like "switch to Umbreon"): Extremely Not Allowed.
Requesting anyone to do any of these not allowed things: Not Allowed.
Revealing what team(s) a tournament player is likely to use in future battles is not allowed.
Impersonating someone during a tournament is not allowed.
If a player catches someone cheating (for example, seeing leaked teams), then the player must report that to the tournament host as soon as possible.