Deer Hunters Net

I have been bowhunting for 3 years and i am might be going rifle hunting this year(if me and my dad get drawn for one of the state park hunts). I will be using a .308 ruger m77 bolt action with a scope. for shot placement should I aim for the shoulders or the vitals. also I am sighted in dead on at 50 yards if i were to have the chance to take a 70-80 yard shot how high should I aim on the deer. last question is what is a good way to properly shoot(form wise) I dont know if I will be hunting from the ground or a treestand yet and i dont have a bipod. any help would be greatly appreciated.