Implementing a marked card protocal can be a great way to fend off those pesky poker cheaters. This method is used to protect against marked cards and is a subtle way to check the deck to see if any exist.
A quick check for obviously marked cards should be performed randomly during deals and a closer more articulate look should be given about once per hour or two.
An easy way to do a semi-thorough check is to flip through the corners cards as if you are flipping through a picture book. This should reveal any crimps or markings and is a good way to ensure the safety of the deck for markings.
Something else that should be watched is players looking at their cards or other players cards too closely. This suspicious activity could indicate that they are peering in hopes of revealing the cards in which they are looking at.