I have always used a mouth call. If you have a good population of crows you can kill dozens in one day. My call is a very old PS OLT brand not sure if they are still available, not sure it matters that much what brand. Probably the main thing is to be camouflaged as possible including a face mask. Crows are one of the smartest critters in the outdoors, but they are a slave to a crow in distress sound. It will take a little practice with a mouth call, there are certain sounds you can make with a mouth call that will send them packing the other way, but if you can call turkeys, calling crows is easy. Once you get a crow on the ground is when the action picks up, it can litterally be a blast. I think a electronic call would have some serious advantages over a mouth call though, being able to direct their attention away from your location would have to be a big help. I have never used decoys either, but I have read where they are very effective, espeically an owl decoy in the middle of a couple dead crows. No calling needed with that set up, the crows that see such a thing will do the calling for you.

Good luck !!