Any of the traps mentioned here work well. I have had the best luck at night, though in deeper water you can catch them all day. If you have access to a dock or some other structure here's another idea: get some fairly rigid wire mesh with about 1/2" holes. Cut a square about 3'X3' It should lay flat and stay that way (more or less) when lifted by the corners. Tie an equal length of tough cord to each corner, join them all about 3' above the mesh, then leave one longer (10-12'). Place a piece of bait (liver, chicken, fish parts, whatever) in the center of the square mesh and lower it into the water. Come back and lift it out of the water every 10-15 minutes. If there's plenty of crawdads in the water, you should 8-10 each time. It doesn't take long to fill your bucket this way. While you're waiting, wade along shoreline with a flashlight and spotlight 'em. Usually when you get them in the light they'll just stop. You can reach down and pick them up. Small ones I just grab however I can get 'em. If they're 4"+, get them right behind the pinchers so they can't reach back and get you. It's great fun. You can also do this during the day by flipping over rocks along the shore and grabbing them from their hiding places. Be ready though, when that sun hits them, they're in a hurry to get out of there. And they can move! I caught thousands of them like this when I was a kid. Used some for catfish bait and boiled the rest. Right tasty with melted butter and beer.