another way (we havent done this one though) is a bucket of water, with a plank across that rolls, so when they walk across it to get a drink they fall in the bucket and drown. I might put some up in my roof...
Before I moved in my husband had a mouse problem. My 2 cats though ... no more mice. Although he did the ruler balanced across the bucket and drowned a few - videoed it even. But they can swim for ages, so he'd be having to kill them.