Perhaps it's from years of birdhunting, mentally marking where a bird falls in an open fieldand doing the same with every deer I've shot. I don't think you need to get down right away and place a marker.What if the deer beds down right after you lose sight if it? If you move in right away...we all know what can happen.I think it's best to wait.As far as looking for horizontal lines and antlers, seems like common sense. Look for those same things while hunting too.