The only advice I'd give, which is probably different than most, would be, buy bigger than you think you need. To dfanonymous; that's probably a true statement about newbs, I know I did when I started doing this in the early 80's. The only problem is, I never got over it!
When my brother started hunting with me, my pack always weighed 10 lbs. more than his!
I just always lived by the adage, "rather have it & not need it, than need it & not have it." 35 lb. base weight really, my food weighs 35 lbs., a case of canned chili, a sack of potatoes, & etc.
I really didn't do much pack experimenting until the last 4-5 years. I started with an external frame Jansport then moved to a Cabelas external frame then a Dana Design(1995?) & then to Mystery Ranch 6500 with NICE frame(2008). In the last 5 yrs. I've tried Stone Glacier, KUIU, the new & not improved Mystery Ranch Marshall, & Kifaru & one more. Don't get me wrong when I say "tried," I just bought them on their 30 day trial period, not actual hunting. Just carried them with weight to see what I liked & how they fit. The Marshall is more or less just MR's foreign made version of their USA made Military 6500 converted with hunting features. Not as good as the MR I already had. I didn't like the SG, it didn't fit me well & the material/straps were not as heavy duty as the MR. The KUIU fit me pretty good(Pro 7800) & I did like it but the straps/buckles were really lightweight, even lighter than SG. The Kifaru was the best quality of the packs I tried(except the one I got). They just didn't make a design/style or size that I liked. Funny thing is, I've come full circle
What I finally settled on this time, just an XL daypack.............