Players are also expected to pay attention to the order of the action and not make any action, including betting, out of turn. Acting out of turn in particularly important because it gives the players still to act behind more information than other players have had access to.
Players can also put out different bet sizes to alter or influence the hand before it even gets to them. The dealer or floor person on hand will be forced to rule on which actions are binding and which bets must be returned but it's better to just not bet out of turn in the first place.