said by rockotman:
Placement of the trap is every bit as important as the bait. Make sure it is placed along a wall, parallel to the wall, in an area that they usually pass through on the way in their search for food.
I will put in another vote for the Victor traps. My wife has had great success in using them to eliminate the mice in her horse barn.
What he said about the importance of placement, and also add a +1 from me for manual traps like Victor.
As for bait I have always used and had VERY good luck with any 'fragrant" (read spicy) meats such as European salami or bits of pepperoni. Even bacon will do in a pinch. Just make sure the bait is well anchored to the trigger mechanism and small enough they won't just eat around the edges.