I have been a member of REI since forever, and they have a lot of good advice.
http://www.rei.com/learn/expert-advice/ultralight-backpacking.htmlI grew up with 30-50 pound backpacks, but with new materials some people are getting by with less than 20. The thing to consider is, for example, how well a really thin groundcloth will resist puncturing versus a slightly stouter one.
I have a two pound sleeping bag, rated to 20 degrees F, but if it gets that cold I don't sleep very well. If there's any chance it might get colder I will always carry my 6 or 7 pound sub-zero bag. I always carry a full-length Therm-a-Rest pad, because sleeping comfort, to me, is very important. If you are young and tough you can probably get by with less.
I prefer completely enclosed tents versus tarps, because more than once I have been rudely awakened by insects crawling on my face, checking out my ears. I have a three-pound tent that erects with hiking poles, but I also have a one-pound bivy sack with poles around the head area so I don't feel like I am suffocating, but there is no room inside for anything but sleeping.
If you backpack enough, you will find yourself collecting all kinds of gear over the years. Generally you start out with summer stuff for your first trip.
I highly recommend getting a copy of "The Complete Walker IV" by Colin Fletcher and Chip Rawlins. This is the fourth edition of what has been considered by many to be the backpacker's "Bible."
