Around here (MS), recreational trapping requires a license (its only $5 though), but "chicken-necked" and netting are unregulated (but there is a size limit of 5" for hard shelled crabs no matter how you catch them).
The string method works great. But the most common method around here is a simple drop net (wal-mart style) with the chicken tied in the middle of it. That way you can often get several crabs at a time and you don't have to constantly tend it. Just lift it up every so often and 9/10 times there are crabs in it (they really LOVE chicken!).
Chicken necks are indeed the best bait, but they will go after any kind of chicken, as well as fish pieces or pretty much anything else smelly and fleshy.
crabs are definitely built for combat, so get a pair of thick gloves or avoid handling them at all costs
net -> bucket -> pot - no hands!!!