At nighttime turn on all lights and walk the perimeter of the house. Look for light coming trough gaps under doors even the smallest gap a mouse can get under. In the house inspect along walls for holes and gaps and droppings. Fills those temporary with steel wool they cant chew through it.
The best traps are the old victory wood spring traps. But they can be a bitch to set. I have tried many the plastic quick set traps but they are fragile. They even say that are one time use. The best of these I have found are the Tom Cat brand as I can reuse four to five times before the plastic trigger breaks.
