Bait them up for a week or two with a mix of corn and cheap birdseed works best with no shooting. Pour it into your spot you want to take them out at (aka set range and I add a backstop). After they are accustomed to the pile, they will usually keep coming despite their buddies TKO'd on either side. If one goes to barking take him out asap. I could take 5-8 per day off the same pile before they wised up. I shoot from inside a small barn. After you have taken out the first wave, keep feeding (add some sugar at this point) and give it another week and then lay waste. Usually after 2 rounds I've cleaned out the neighborhood for a while and my pecan tree is safe. If ya get a bunch of short tail youngins its on like donkey kong.
edited: Later in the summer as the pecans start to fill out start to add chopped pecans if under a pecan tree, I'll candy a few pecans in a pan and chop them up. It catches the smarter ones. Vary your shooting locations and times you shoot. The smarter ones will pattern you even with the can (I'm running an AAC Element2 with CCI quiets). If they start to get smart on the barn I'll move to longer shots or throw up some tarps to hide movement.