No matter what helpful info you get in CS, the best thing to do is probably to take your camera and accessories (whatever you will bring on a typical outing) down to a well-stocked shop, eg. Cathay Photo, and just spend some time sticking all the stuff into the various bags they sell until you find one that really appeals to you.
A camera bag is a pretty personal thing ... different people have different needs even with the same equipment to be dumped into the bag.
I'd just like to add one more thing ... get as small a bag as practical. What you can't fit in, you may not use anyway, so just leave at home. When you upgrade camera, upgrade bag as well. But that's my own personal opinion