Learn about the firearm you intend to hunt with. What kind of ammunition it uses, what game it is appropriate for use upon, how it functions, what it's component parts are, and what they are used for.
Spend time improving your marksmanship skills with that firearm prior to opening day.
Study the type of game you intend to hunt. Learn about it's biology, it's habitats and behaviors. Become familiar with the most effective body target areas that will produce quick and humane kills.
Study woodcraft. Know how to navigate in the woods. Visit and scout the area you intend to hunt in. Learn about the flora, other fauna, and the terrain.
:-)