Biggest mistake I've made (off the top of my head) is staying too long in an area that doesn't hold many elk. It's hard (for me at least) to leave an area that is historically good or has been good early in the season, even if I'm not seeing elk anymore.
#3 failing to realize that a mature bull can walk behind a thin tree and never come out the other side
Yeah, big bucks will do that to. Hell, little bucks will do it if I've decided I'm going to shoot them when they come out
