I am becoming more and more convinced, through personal errors of my own, that movement (or better- lack of movement) on stand is the number one key to success, more so than camo. It is also my weakest point. I would then say scent control, because every now and then, by shear chance, the wind will work for you even if you're not paying attention to it, but movement can/will get you busted regardless of anything else you did right.

So, I would go:

No movement
scent control
camo
treestand cover (tied with camo)
treestand Height

I leave smoking off because I don't do it so I don't know the effects, except that besides the odor you have the movement of your hands, which is bad. I don't know if the sight of the smoke cloud would spook a deer or not, or the odor of it.