Don't look to hard, I never look at places I actually frequent. If they are posted I walk. If they are not I assume that they are ok with carry, if I am asked to leave, I walk.
I know I used to try looking for signs or anything but figured if they are going to make me look for it they aren't too worried about keeping me out, so I just go in and go about my business. So far no problems, but if I do end up having a problem my wife knows we'll be walking right out the door and not coming back. She fought me on that policy at first but she has completely come around with me carrying and not shopping at places that won't allow me to carry.