Most major poker tournaments, and many small ones, use the set of rules put out by the Poker Tournament Directors Association. For people who play tournaments on a regular basis, it’s worth being familiar with this rule book, so that situations don’t catch you by surprise.
The newest edition of the TDA rules was just released last week. Many of the changes are minor improvements in wording, highly technical, dealing with extremely rare circumstances, or instructions on procedures for tournament staff that players don’t really need to know about. Let’s ignore those, and focus just on the ones that substantively affect all players.