RE: aiming from your tree stand
The guy I've been hunting with this year and I have debated this all year long: he says aim low, and I continue to aim where I want my arrow to hit. I told him I can pick out any leaf I want to from my tree stand and nail it, so I should be able to do the same with a deer.
For proof, I've released four arrows at whitetails this year, and I've got three in the freezer and one in the back of my truck right now. I say aim where you want your arrow to hit.
But, above all, practice, practice, and practice.