When Will and Jimmy are playing chess, we see one player capture the other player's queen. A few moments later, the player who lost his queen still has it. From the board position, one can tell the game is still in the opening stages, and so an endgame pawn-promotion-to-queen (to get another queen) is highly unlikely. And since it was a serious game with a clock, it is also highly unlikely that one player would allow his opponent to take back his move, saving his queen.
The day before she is attacked, Will and Laura see a report on Bourdette's death on a TV at the hotel bar. Later, one of the cops mentions that Laura was raped last September. But when Will watches the DVD interview with Bourdette that was recorded moments before his death, Marsh says it's November 3rd.
When Will bought the bar from the vending machine, the first two numbers were 11. This should have made the same sound when pressed. Instead, it made two different sounds, and it appeared his fingers moved not to touch 1 twice.
When Simon enters the toilets in the sports stadium, a man with a striped top and distinguishable facial hair can be seen entering behind him. A few moments later upon leaving the stadium the same extra can be clearly seen opening the door for Simon, only this time wearing a security uniform.