Well first I`d like to suggest that you go out to barnes and Noble or your local outdoor store and pickup the Backpacker Magazine Gear Guide for 2009, which just came out this month. They have tons of gear reviewed from backpacks, tents and boots to stoves, headlamps, and sleeping bags. They may even have it up on their website: www.backpacker.com
It`s hard to say how many cubic inches you will need for your backpack because there are a couple of variables. What will your average trip length be- mainly weekend trips or weeklong to weeklong+ trips. Also the time of year that you will be hiking also obviously you can get away with a smaller backpack in the summer than you could in the winter because your clothes are heavier in the winter time, so take that into account. I myself have a spring/summer backpack and a fall/winter backpack.
The backpacking brands I would look at would be Osprey, Gregory, Mountain Smith, Kelty, and Deuter. The REI Flash 65 won the editors choice award for most versatile backpack. But the best pack for you is the one that fits you comfortably. Remember when trying on backpacks to add some weight to it, trying on an empty backpack does nothing for you. Fully adjust the pack first, any good employee will surely help you with this. It`s just like when you buy boots your bring the sock you will be hiking in (hopefully not a white cotton sock, but rather an actual hiking sock) this way you know what it`ll feel like when it comes time to put those socks and boots on.
Were you asking about the other gear too or just about the backpack? Again I suggest you go to the store look around a bit an dthen buy the Backpacker Gear guide from the magazine rack. I`m not sure how old you are but if you are under 18 look to join a scout troop that does backpacking. Troops usually have things like tents and stoves for the troop to use. It`s a great way to get familar with gear and to become comfortable in using it under a controlled environment. If you are over 18 you can join a Venturing Crew that is like co-ed scouting but they tend to do more age appropriate trips.
If you have any questions feel free to email me.