Acting out of Turn Deliberately
This kind of mistake can also lead to much more serious problems in a tournament situation. In a cash game, one player improperly acting out of turn can cost another player a few bets, or at most the whole pot. But in a tournament, that same mistake can cost another player the whole tournament. In a No-Limit poker tournament, any single action can be a crucial turning point, a do-or-die situation. Rules differ from one tournament to another, but generally the out-of-turn action will be considered binding, unless the player who was originally supposed to act first decides to make a bet or raise.
Usually acting out of turn is an honest mistake, but sadly some players will do this deliberately, to give themselves an unfair advantage. This is a kind of angle-shooting, or dirty poker. An example would be if a player declares “raise” before it’s his turn to act, in order to induce the players in front of him to check their hands. Then when they do, he checks along and gets a free card. If you see a player acting out of turn repeatedly, there’s a very good chance they are doing it on purpose, and in that case you can and should complain to the floor-person. Acting out of turn is a violation of the rules in any card room, and repeat offenders will be subject to penalties.