For crows I have about 6 crow decoys and one owl decoy. I like to set up on the edge of the woods in a spot with shorter trees than the rest of the wood line so the crows will come in lower. I usually put 4 crows on the ground and two on tree limbs. I have called in the woods but the crows tend to light in trees just out of range and look things over and that's usually a bad thing. I have called from pretty clean fence rows also and that worked well but there are no fences where I normally hunt. My all time favorite setup is about two rows inside a corn field.
i use a mojo crow and about 6 regular ones hang the mojo from a low tree branch it will spin and turn. my favorate place is a cedar thicket on top of a ridge find a little open spot that they can see movement when they fly over. when you shoot one the others think that they just joined the fight and divebomb in after them , if its a foggy morning you can shoot for ever .also go near dumps when the weather is snowy or the ground is frozen they are stacked up like cord wood. take plenty of shells and stay hid.