The best weapon when rat hunting depends on how you are hunting them. If still hunting, a good 20 gauge is good.

If you are flushing them, you need a few friends and a good shovel to hammer them with. Someone needs to flip over boards, etc that they are hiding under and the others swap them. Make sure you don't get hit with the shovel. A good dog or two helps to get the ones who are runners.

As far as places to hunt, the best place is in a barn when the big gopher rats come in to feed on the grain. A good cold snap will make them migrate and get them moving into shelter.

The most ultimate place to hunt is in a hog house, you will find rats that are no b.s. a foot long, not including the tail. I am not sure of the trophy measurement for length and girth, but those are some BFR's.