If you bait with peanut butter, and find that the mice manage to get it off without springing the trap, try buttering some on the UNDERSIDE of the bait tray, as well as some on the top. They just can't leave well enough alone, they have to try for that last bit, and there isn't room for a mouse's head under the tray.
This PTG archive page provided courtesy of Moy Piano Service, LLC