Greg, last year I hunted a spot that was a 20 foot rock pile that is growing stuff. I tucked myself between two wild rose bushes, and used a cut log that had been pushed up there for footing. The first buck came on the 20 yard trail, stopped, looked directly at me. I could tell that he never saw me. I had back cover and cover to the side of me that I was tucked up into. He turned his head 180 and I shot, but I shot slightly high to avoid high grass. That was my mistake because he broke his knee and lowered himself 8 inches. The arrow passed over top. He walked away.
I left the area for a week and came back. The next buck came on the 8 yard trail. Too close. He heard my arrow slide across the riser. He jumped 25 yards to the side, turned and looked at me. He never figured who I was. He walked away too.
The biggest key is back cover. You gotta have that. Then cover in front and sides and/or top is good because that creates more and more shadows making it more and more difficult for the deer to see you and also to figure out what you are.
I highly recommend G. Fred Asbell's book "Stalking & Still-Hunting." In fact, for me, that book solidifies what traditional hunting is about. And, even though his treatment of ground blinds is not complete, he does lay down the basics of the concepts, to me, of what it is to be a predator - which is disappearing as much as possible into the natural environment around you. I view a good predator as simply being an opportunist. So, an opportunist looks for a setting where his stealth will be better than another place. And, if you can improve on what nature gives you, then fine, you do it.
I hope that helps.