To protect against cheaters, the deck can be changed every once in awhile. I suggest changing the decks at least once an hour to keep a game honest. At any card room or casino you can simply request the deck to be changed. Some places only allow you to change the decks once during a certain time period, sometimes every two hours.
Changing or swapping the deck is effective as a use against marked cards and is also a good checkpoint for a card count. This can prevent players from cheating because they know that you are on top of things and that somebody is watching very closely. It is always a good idea to suggest that the deck be swapped whether a cheat is suspected or not.