I too was a 1 day first-timer 8-17-11. I'll share and compare some of my Whitney Experience: I carried a snack pack on my hip with GU Energy Gel, little packs of cracker snacks, small Snicker bars, small Cliff bars, and plain MM's. I carried a 30 liter day pack but when I took breaks I preferred not to sit and not to take off my pack so the little pack on my belt worked great. My GU had caffeine and as far as I know I had no problem hydrating. I carried 3 1/2 liters of water from the start, filtered and filled at Trailside Meadows, and filled without filtering at switchback 23 on the descent. I wore lowcut Goretex trail runners with no ankle support and my feet were fine (except for several black toenails-I traded in my shoes at REI for a half size bigger when I got back home even though I had worn them for a season and a half, I guess that 11 mile descent is hard on the toes)I did bring extra socks but didn't bother changing them. I find trekking poles essential after using them for the last 2 years. Before that I never did. They take a load off my knees and ankles and keep my hands elevated above my waist. Before I started using poles my hands used to swell up while hiking but with the poles I do not have that problem. I mentioned this on my TR: I preloaded Ibuprofen starting 2 days before my hike and the day of the hike. My joints were fine the whole day (I'm 60 yrs old and a couple of years ago my knees and ankles ached going down hill. Maybe I get some relief since I started taking a Glucosamine supplement about 6 months ago.)