1. Big pack. Recommended: NorthFace or Military Issue surplus. Make sure the straps have plenty of padding for your shoulders. How the pockets are arranged is up to you.
a. Make sure you have two of everything. One to wear and one to pack.
b. Outerwear. Make sure everything is at least one or two sizes too large for you. Adding layers is the key.
c. Innerwear. During cold seasons, this is vitally important. Again, two of everything. During hot weather, this is conspicuous by its absence. Heat rash or its equivalent is not only wearisome, but painful. Medicated powder is essential. Gold Bond, or its equivalent; in small containers. 
d. Boots and shoes. The best, waterproofed boots you can afford will be worth their weight in gold. Try good sturdy sandals for wear around camp, light weight and cool. Remember the powder? Here is where it can make or break you. If you don't take care of your feet, they can't take care of you. This can become a full-fledged emergency if you're alone.