What we are trying to do is keep the bait from spoiling, and just like any other food product, it might spread disease and cause illness. So if you have children with you we suggest that a parent handle the bait in the process of crabbing. The crab usually smells the bait in the water long before he sees it, and follows the scent trail in the water to find the bait. If the bait becomes old, which it does quickly, it won't give off a very good scent trail and the crabs won't find it or know it is there. That's about it except for tossing the bait into the water, and then tying the other end to something, or you can hold on to the string.
Most people put more than one line in the water to increase their chances.
Sometimes you will even catch two crabs on the same piece of bait, but usually those are only really small ones that you shouldn't keep. Once you see the line moving away or becoming taught because the crab has the bait, start pulling the string in very slowly. Often there will not be any resistance to pulling the line in, but there will be a crab on the bait. The crabs don't really get caught on the bait, they just don't want to let go. Using this technique the crab won't become scared when he sees you put the net in the water because it will already be there and he will think it is natural.