I have been finding out the hard way "not to back up." By backing up we leave behind, however small, a bit of scent. This scent lingers perhaps the most along the ground. On a couple occasions I have advanced still hunting, cross or up wind, looking for a good ambush position, and have "backed up" to what I thought was the best place. Well, the places were good, except that I left infinitesimally small amounts of scent ahead of me.
Twice in a row the creatures I wanted to put in my freezer hung up where I had been. We too easily forget (at least I do) the incredible sense of smell these (big game) creatures have. They may not smell enough to bolt, but they may smell enough to get uncomfortable, raise their alert level, or stop (hang up), and not give you that picture perfect shot you were hoping for. And remember, a big game animal spends a fair amount of time with nose along the ground. While the wind may have taken most of my scent away - some got left between the blades of grass and pine needles.