I save all the heads and tails off the salmon I catch. If out of salmon I use chicken or turkey. As for how deep depends on where you crabbing at and where the crabs are. Incoming tide I usually start at 35 feet by the time I pull them out they are usually deeper but 40 is what I am trying to target. Most of the crabbing I do is on the lower hood canal near tahuya. If you have a fish finder look for an area where you have flats dropping off to deeper water. If you dont have a fish finder or havent crabbed in an area look for where other people have theirs at hopefully they have more experience in the area. I will drop at 30 and 40 and 50 feet and the pot with the most when I pull it up. Is where I will set the rest of the pots.