My best partner had 4 paws, even if he couldn't sit still in a blind.
As AK Ironworker put it, attitude is almost everything. I think another piece of it is physical fitness. A lot of people are just too out of shape. Hunting, even from a 4-wheeler is a strenuous activity that is sustained for several days. I think this is why the road system is so heavily hunted.
Personal habits are important, too. I can't/won't be around, especially in close proximity, people who smoke, drink, use drugs, etc.
You could probably throw work ethic in there, too.