it also can help to "chum" them a bit with whatever kinds of bait you will be using. start scattering a bit of it out for them as a 'free buffet' a few nights before setting the trap...that will help reduce the suspicion of a 'new' food offerred in a stange new way (the trap). If they have already expienced enjoying that food safely, they will be less wary of seeking it in the trap.