1) Buy your pack last if at all possible. You will want to get a feel for what gear you *do* want to carry first, and buy your pack to fit that gear. Otherwise most people fall into the trap of buying something too big "just in case" and too expensive.

If you can borrow a pack - great. do that for the first trip, and concentrate on getting yourself a relatively lightweight comfortable set of gear to carry in the pack first.

There's an excellent "18 pound 3 day" gear list you can have a look at on this parent site (www.backpacking.net). it should give you some ideas. Mine is posted in my signature.

When you have a peek at mine, bear in mind that if I roll up my blue foam pad and carry it outside the pack - I can put tha t list of gear, and 4 nights food in a 30 litre(1800 Cubic inch) daypack. That doesn't mean you need to go that extreme right away, just bear in mind that you may not need a metric ton of gear in a huge pack to be comfortable if you think about it carefully.