A compilation of suggestions and tips from successful thru hikers (mostly from recent email correspondences):
"For clothing, I'd highly recommend buying as much merino wool as you can. Merino wool is amazing for a bunch of reasons. It keeps you cool when it's hot and warm when it's cold (even when you're wet). It's very odor resistant. My friends and I would hike 5 or 6 days straight and my unwashed clothes would smell better than their freshly washed synthetic clothes. I still wear my wool hiking clothes from my thru, and I can assure you theirs have been tossed into the garbage."
"In an effort to save weight, I got an extra-small sleeping pad, which only reached down to my butt. This was great for the warmer weather, but horrible when cold because my legs froze on the cold ground."
"I recommend wearing lightweight, wicking running shorts instead of actual "hiking" clothing. The running shorts dries much faster, weighs less and overall more comfortable"
"If I could do it over again, I would have carried a Kindle with me rather than actual books. Kindle weighs less. And I often finished my book before reaching the next town, which was very frustrating and wouldn't happen with a Kindle (read lot at night before sleeping)."
Food & Mail Drops
"My advice is at first (till you get food supply down to a science), carry "emergency food" that you haven't built into what you think you need between towns. For me, this was a packet of Raman noodles and a giant protein bar."
"I recommend AquaMira drops for purifying water. Pumps are heavy, I saw a number of SteriPens break on hikers, and iodine tablets taste horrible."
"Here are a few things I recommend getting in mail drops: roll of toilet paper (seems they only sell the rough stuff one at a time in the stores), however many multivitamins needed to get you to the next mail drop (weighs less than carrying big bottle of them), proper number of pain reliever meds (again, lighter than the bottle full), pre-measured protein powder in a zip loc, pre-measured gatorade powder in a zip loc, needed amount of calcium chews (because of the beating your body takes, especially as a woman), any food you need."
"I bought all of my food along the way, and yes mail drops are a hassle. I used a bounce box for my laptop, camera batteries etc and it was such a pain trying to guess where you'd be in 2 weeks and then rushing to a town before the post office closed."
"Take your time in the beginning. The hikers I saw fall off the trail with overuse injuries were the ones that from Springer were trying to do 17 - 20 miles a day. Just listen to your body"
"Don't get too committed to hiking with one person or one group. I saw lots of people mess up their hikes by hurrying to catch up with friends or waiting around for friends to catch up. It's funny how bonded people get, and how quickly. Just move at your own pace. You will make amazing friends, and they will still be your friends after the hike is over. "
EDIT- Post hike, this is my FAVORITE piece of advice:
"Nothing is ever as bad or ever as good as people say on the trail. You will notice people trying to convince you that you are going to die in the Smokies, for example. Just make your own judgements and don't over-plan or expect anything too extreme to happen. "
"I wish I'd paid more attention to deteriorations in my gear and in my health. On the trail, little things tend to turn into big ones if you neglect them."
"The trail is close enough to civilization so you can make new decisions (about gear, food, etc.) as you go, so don't worry about figuring everything out perfectly ahead of time."
"It's funny how the brain works and what this trail does to you. I only look back on my experiences in a positive light, it's like I forgot all the pain and misery or maybe I like it?! You'll know what I mean once you finish the trail (notice I said FINISH!). Seriously, short of actually having a major injury, this thing is pretty much all mental."
"I would suggest starting mid week (as opposed to on a Friday, Saturday, or Sunday) to avoid the huge crowd and also, to be a bit later."
"Here's a random piece of advice: pee rags are awesome."