I'm fairly new to hunting, but I've spent a bunch of time backpacking and generally being in the woods.
1. Always have a map and compass when you are on unfamiliar land (and it's good even if you know it well). And know how to use them.
2. Gatorade bottles are stronger and quieter than the bottles of water sold in gas stations, and lighter and cheaper than Nalgene or army canteens. For best results, keep a clean Gatorade bottle that you fill with water at home, since there is too much potasium and sodium in Gatorade if you aren't active and sweating. (And even then, it's still a bit much! Alternate one Gatorade with two waters.) If you hate the taste of water, mix something in it.
3. Pack light. You're already carrying a gun and ammo, plus other hunting-specific gear. Make sure your pack is light and your knees will be much happier. Aim for total weight of less than 1/5 of your body weight, or less than 20 lbs., whichever is lighter.
4. A pound on the foot is worth five on the back. If your shoes weigh two pounds each, it is the same as going barefoot and carrying twenty pounds on your back. It is especially true for people with longer strides.
5. Take care of your feet, and they will take care of you. Wear wool socks that absorb odor, wick away moisture, and keep your feet warm even when wet. Treat blisters immediately. Make sure your shoes or boots fit well and aren't too stiff or heavy. Opening day is a terrible time to break in a new pair of shoes or boots.