most important
 

Mental preparation see your self accomplishing your goal during
practice practice practice!

I think the most important parts are mental. Understanding the animal you are hunting, its habitat and your own role and responsibilities.

most important
 

Hmmm, I think the #1 most important thing is practice.

Follow through. Don't jerk the bow from your face after the release to see where the arrow hit. I think this equates to a lot of misses.

shot placement

#1. practice
#2&3 tie. Broadheads and arrows. This is the only part of the entire set up that actually kills the animal. If these two things aren't up to par nothing else matters IMO.

Brand of bow means nothing. Any bow can and will get an arrow tot he target accurately if the shooter is willing to practice with said bow.

Breathing technique - great for shooting off the line but in a treestand while a big buck is under you is something else.

Stance - Meaningless in a treestand when you are trying to get a shot off at a deer behind you or around a tree, etc... CHances are your stance isn't going to be anywhere close to how you shoot in the back yard.

Tuning your bow so that unfletched arrows, fletched arrows with field points, and fletched arrows with broadheads all shoot the same, and practice.

Practice, practice, practice
 

I first came out of the basketball arena. Shooting foul shots at baskets is a lot like shooting arrows at targets.

Concentration, form, repeated performance(doing it over and over the same way) and others need to be practice. They don't happen by magic.

An inaccurate archer who is hunting n the woods is a wasted life.

Preparation:
Practice and Set-up- Become Proficient and confident in your archery weapon. No matter who the manufacturer of the bow, arrow, broadheads,release, etc. is
Scouting- Know where the deer are and what their patterns are.
Comfort- Ready for long days in the stand and whatever weather you encounter.
Range- Know the range of landmarks from your stand.

Besides the above....
Persistance and Patience are very important, without these you will never be consistently successful.
Ability to adapt as the deer's patterns change and hunting pressure changes.
Your stance will differ greatly when in a stand compared to a range due to obstacles like leaves, twigs, other animals. Your mental checklist should remain the same but body position often changes.

1. Being able to hunt deer to get a high % shot opportunity.

2. Proficiency with your bow at your max range and staying well within it.

3. Not taking advice from TV hero's given in their 30 minute infomercials.