There are a couple of different ways I like to catch blue crabs and I'll give you some information on each!
Use a string with a piece of chicken, beef pancreas, or anything bloody that will stay on the line! Make your line about 10-15 feet long. Tie your chicken, etc on the end of your line. Throw it out and then attach the line to a rod, pole, chair, or even a bunch of grass. Gather the grass up and tie it around. Crabs don't pull very hard so just about anything will do! You will use a net to catch them!
Using a trap is another great alternative! Especially if you enjoy fishing while you are crabbing. You can throw a trap out and just let it sit while you fish! I use my very own Commercial built crab traps! I make and sell these so you can check them at https://www.rollincajuncrabtraps.com. I sell them on marketplace so go take a look if you are interested!
You can use the same type of baits inside these traps as well! I normally use chicken because it's cheap! A bag of chicken leg quarters goes a long long way! Stuff it inside the bait box. Tie yourself a rope to your trap and throw it out! Always make sure the trap funnels (holes where the crabs get into the trap) are always at the bottom when you throw it in!
However, you decide to catch blue crabs it is always a fun time! I love a good outing and crabbing adventure. You can actually see some videos of me catching crabs on a string from my YouTube channel! I also teach you how to catch them! https://www.youtube.com/c/RollinCajunOutdoorsYT