When I was a kid we used to catch and eat them. They are tasty but a lot of work to clean.
We just used nylon string with a large hook tied to a milk jug. 18-24" of string will work. We found chicken gizzards were the best bait for staying on the hooks. Let them get ripe before you put them in the water. If you have a lot of cattails, the turtle will usually crawl into a mess of them. It can get exciting when you wade into water, grab the jug and line and then reach for the tail when you determine where the head is.
If you tie a line to shore, make sure the the stick is actually a root or tree branch. A big snapper is powerful and can pull hard on your set up. The jugs have a higher catch rate because they give when the snapper pulls.