I know a lot of folks have luck with peanut butter but I never did... they just seem to pick it off without tripping the trap.
The best bait I have found is chocolate chips. Put a few in the microwave to get them soft then take a knife and get a glob onto the trigger... making sure not to "glue" the trigger to any other parts of the trap. Once the chocolate chip cools it is difficult to get off the trigger. When the mouse starts working on it - nibbling, pulling, etc. - SNAPPO!! Better luck with this method than anything I've ever tried.
Good luck. I haven't had any with my new trailer but had them in my old trailer. Never kept any food in there but I guess it was just a nice place for them to sleep and raise a family. Opening up the drawers with the dish towels and finding a mouse hotel always was a treat.
By the way, I agree about not using the glue traps. Look, I hate mice as much as the next guy but I never checked my trailer every day. When I used glue traps and would go in and find a mouse that was near death, having struggled for who knows how long, it really bothered me. I'm all for killing them, but want it to be over reasonably quickly and painlessly. Call me a bleeding heart, but the glue traps just cross the line for me.