Earth worms, Night crawlers and Red wigglers. I live in a very rural area and just collect my own. Or buy from a local that sells them for bait.
I just chop them up in bite size chunks and feed them a piece at a time with tweezers but you dont have to do it like that. Thats just what I do.
I chose to do it like that so no certain fish would get to much at one time, they will over eat if you let them.
My only worry with that is parasites. I've heard of cases of people having problems with wild caught worms. I live in a pretty rural place myself so I might consider this though.