I have klled deer downwind,I think deer show up from a direction other than what I have set up for many times but not really unexpected,because where I hunt the deer have too many bedding and feeding options to chose from,I believe that to really know where the deer will be coming from you have to have a specific bedding area and a specific feeding area that the deer are almost always using,and all bets are off if you or someone else contaminates that area,like someone else said try to be as scent free as possible and hunt your set.It is alot easier to know where the deer are coming from when coming to a food plot than hunting deep in the timber.