The wiki has an
excellent packing list that really helped us a lot.
If you plan on doing any sort of hiking/walking, I definitely recommend a camel back. We did the water bottle thing and even with convenient sport straps, they are just a nuisance. Infinitely more manageable to just distribute that weight and not hang it off one side of your body. Also, since a backpack is a good thing to have while hiking anyway, it efficiently combines items and keeps the number of straps you're wrangling down.