#1 LUCK
#2 LUCK
#3 More LUCK
I've had plenty of times when I've done everything "right" and still hear the story about some dude who never practices with his gear, walks 100 feet onto public land, no scent control plan whatsoever, starts smoking cigarettes and winds up popping a huge buck that walked right up to him.
But seriously if you implement the ideas already posted, you should be making your own luck. Count me in with the crowd that can't put a specific order on the importance of each.
