What JimmyS said.....plus underestimating the deers ability to see your slightest move IMO.

Not getting home from a hunt when they promised to, and there by incurring the wrath of the wife/girlfriend, which in turn minimizes future hunting outings.

not spending enough time in the woods prior to hunting season, you need to scout the deer to see where they are coming from and what they are going to and why, and how they are getting there.

then you can figure out the best spot to hunt based on a deer's need's...cover, food&water, and the ladies.

Other than proper scouting (i.e. plenty of deer sign but it's from nighttime activity), I'd have to say is not checking the equipment. My rifle got off between regular rifle season and the late season rifle and it cost me at least three deer. I learned my lesson in my "dream season." Always check your gear to make sure everything is right and working properly. 5" at 50 yards cost me venison in the freezer.

fallin asleep

Doing something dumb or unethical because of pier preasure

dd

Above all else, I would say poor prep work before going into the field to hunt. Generally not knowing what your deer are doing before trying to hunt them.

I dont think playing the wind is possible... If you sit around a fire for a couple of hours you will notice the wind (watch the smoke) will change directions too many times to keep up with. Some mistakes ive made is not wearing a safety harness in a stand( No Biggy), Not plugging a shotgun when your supposed to ( sorry game wardens, Ill make sure i do), Shot a deer with a shotgun thats not sighted in completly( Hit it in the head at 75 yards after 5 shots aiming at the lungs) Im sure there is a few others if i think about it but i have to run to the little boys room for a quick drop off of the kids!!!!

Not staying in your stand.or oversleeping and getting in it too late.You chose that spot for a reasion,stay with the plan man!

not scouting enough to know where the best places are.