I've read the mailing list, I've joined the online groups, but there's still a lot I've learned after starting hiking. Here's a list of some of the things I've found around using my gear, hiking, and just plain old technique that made doing the PCT easier for me.
Too Much Food: A lot of people send far too much food to themselves in resupply packages. You won't be eating 4000 calories a day in the first day or week or weeks; you'll be burning off body fat. Even though I started early, there was already quite a bit of unneeded food in Warner Springs from the few hikers that had gone before me.
Hunger: Along with the 'too much food' is the hunger. There's a lot of chatter about 'hiker hunger', but I've only felt faint pangs, even after five weeks. I can eat quite a bit now though and not feel full.
Campsites: Campsites are more numerous than those listed by Halfmile or in the Guthook app. I've put up my tent in more places that are unmarked on both sources.
Rest Days: I didn't take enough rest or zero days when I started, and just felt worn out after about six days. My first overnight motel stop was in Idyllwild--my eighth night on the trail. I try to look for a comfy bed every six days or so.
Trekking Poles: I've never used trekking poles before. It took a day to get used to them, now I think they're awesome. I use the Black Diamond 120cm Z-Poles with replacement Leki tips. I like them because they're very lightweight and I can collapse them while walking (for instance, for walking on a road). I took off the straps too, and will put snow baskets on for the High Sierra.
Lightweight gloves are great: I almost didn't take my ultrathin Under Armour running gloves, and am super happy I did. I wear them all the time when hiking--they keep the sun off my hands, keep them warm when it's cool out and cool when it's warm out, and are good around camp when it's not cold cold. I've seen other hikers wear Pearl Izumi cycling gloves, which is another choice.
It's cold and windy: I started the PCT early on March 17th, and it's been fairly cold at night, which I was somewhat prepared for. About half the nights have been just above freezing, and maybe a third have been just below freezing, with a few cold nights in the low 20s and a few mild nights in the 40s. It's also been windy at all times--days, nights, whenever--and the wind is never pleasant. This hasn't been summer hiking weather at all.
Be helpful but not a babysitter: Yes, if you're out of food I'll help you out with a Clif bar. Yes, if you're stupid and only brought 2 liters of water for the 35 mile waterless stretch north of Highway 58 I'll help you out with a half liter. But you should've known better with your food, and read the warning signs about "35 miles of NO WATER." I didn't come on the PCT to babysit the unprepared or the misprepared (the guy who couldn't snuff his alcohol stove falls into this category.)
The PCT is mostly well marked: There are marker poles most everywhere, and it's easy to follow, except when it isn't. You miss a marker, particularly if the trail goes along a dirt road, and you might not realize it for ten or 20 minutes. In some places (like above Highway 58, roughly mile 575) the PCT goes along a jeep road for many miles with no PCT signs at all; the ten mile walk along the LA aqueduct also doesn't have many signs at all.) Some places also don't have obvious PCT signage (Mt San Jacinto State Park above Idyllwild), other parts of the PCT have confusing parallel paths (the dirtbike tracks around mile 560). You can't always depend on footprints, which may be local hikers. I haven't felt a need for a compass or paper map, my GPS and iPhone apps are reliable (and back each other up, as it were).
Footcare is important, yet feet do adapt: I had blisters the first hundred miles, but they strangely weren't painful. The next hundred miles I did have painful blisters, and they harded up and went away. I don't think shoe choice is all that important--one shoe manufacturer says "give your feet two to three weeks to adapt to our new Natural UltraStride(tm) fit" but that's just marketing hooey, in two or three weeks your feet can adapt to most any shoe--and if those shoes aren't working, try something new. It's hard to tell what'll work before you hike for three weeks with 30 or 40 pounds on your back.
My backpack is fantastic: I bought a ULA Catalyst for this trip, and I really love it. I especially like the side pockets, which fit the 1.5L SmartWater bottle, the hip belt pockets, and the outside mesh pocket so I don't have to open the pack during the day.
Packing my pack: I got rid of a lot of stuff sacks, and now have three regular ones, plus a drybag stuff sack for my sleeping bag. Clothes go in the gold one, misc items go in the blue one. The green one is the 'go bag', when I'm getting ready to go in the morning I'll put my hat and sunglasses and snacks in it and set it outside the tent, then pack the rest of the items and the tent in the pack. Once the pack is all packed, I dig through the green go bag and distribute all those items. I used to put the sleeping bag on the bottom, then the tent, then food and the bags, but that really made the pack a bit top heavy. Now I put the heaviest items on the bottom--food and then clothing--then the pot and stove, the camping gear. I put the sleeping bag around them and towards the outside, then the tent on top with my down jacket and rain jacket. That's much better distribution, and all the weight ends up around my waist generally, so my shoulders and back feel better at the end of the day and I'm not as hunched over. When I get to camp I just take the tent poles off the outside of the pack, and the tent is right there on top for easy setup without digging all the way to the bottom for it. One more bonus: if the tent is packed wet in the morning, I can easily pull it out at a break for drying out.
Ultralight is overdone: On a lot of the forums and groups, I think there's too much emphasis on choosing super-light items; one guy was wondering if he should get a heavier headlamp that weighed 0.2 ounces more, but had rechargeable batteries. That's the weight of one US nickel--it's not going to kill you. Grams add up to a few more grams, ounces add up to a few more ounces. It's great that there's so much ultralight gear available now, but it's really reached the point of diminishing returns. It's really the heavy water carries and the week-long supply of food that'll get you; you'll need to carry six or seven liters of water across a few long dry stretches, and maybe eight or nine days of food (say, 12 to 14 pounds) in the Sierra. Your pack will weigh around 40 pounds at certain points, despite all your ultralight choices. Get your pack weight (without food or water) in that 16 to 19 pound range and you'll be fine, and don't obsess or spend too much. The point of ultralight isn't to hit some target weight, it's to make yourself feel more comfy on the trail. Don't skimp by leaving out something that makes you comfy, like longer underwear or a less cramped shelter. Suffering through several below-freezing nights to save a few ounces isn't worth it IMHO.
Anti-Chafe: I'm super happy I brought diaper rash ointment for the first few days. At Super Daves in Mt Laguna I bought anti-chafe and it worked well too.
Pack a clean towel and a disgusting towel: I have two towels, a larger one for drying things like dishes and my hands after washing, and a smaller one that I use to wash my dirty feet and private bits. That smaller one gets disgusting quickly. I cut a section the size of two credit cards off the big one so I can wipe my often runny nose.
Long Pants and shirt FTW: I usually wear shorts when hiking, but on the PCT I wear long pants. They've been great; I don't get sunburnt, and don't get poked by overgrown bushes and such (though most of the trail is well maintained.) I can also spot the ticks easier; I've had three on my pants but none have gotten through. I also used to just wear T-shirts, but I switched to wearing just a long sleeve white button down shirt a few weeks in. That shirt is great--it keeps the sun off my arms, when it gets hot I can unbutton it and untuck it, letting it billow around me like some 70s rock star, and when it's cold I just button it up. The shirt is good for hiking in most any temperature above 45 degrees.
The parasol: Yep, I thought the umbrella would be handy but not loved. Wrong. I love the umbrella, and used it frequently when it got above 80 degrees. It kept the sun off my entire upper body, and I tied it into the backpack so I could still use my hiking poles. (The model I have is the EuroSchrim Handsfree.) It made certain sections much more pleasant, like the section F desert, and reduced my water consumption as well.
Water consumption. My water 'burn rate' was right around 1 liter per 6 miles, though on hot days it was more like 1 liter per 4 miles. After the first day, when I ran out of water a few miles short of Lake Morena, I've often been carrying more water than I really need, but that's OK. I just tell myself "one liter of water weighs just about the same as the bear canister" so I pretend I'm really practicing for the heavy carries of food in the Sierra.
Miles per day. I guess I was more fit than I supposed, I've been doing around 20 miles a day. Some days are less, around 17, sometimes I get up to 23 or 24 if there's a motel room to get to at the end of the day. I'm paying more attention to elevation than I thought I would, there's a lot of up-and-downs and I don't want to end the day on an up note, as it were. After hiking 16 or 18 miles, the last thing I want to do is climb 2000 feet. It's just better to tackle that in the morning when I'm fresh and it's cooler and shady.
Buy as I go is a big win. Plus Amazon Prime does great resupply. I'm buying as I go; I don't want the hassle of having to plan my schedule around post office opening hours for these small post offices; many aren't open except Monday through Friday, 10 - 4. It's worked out really well so far. For more esoteric items (I broke my keyboard), I've had Amazon ship to a motel once and that worked out well with the two-day shipping option with Amazon Prime.
Camp Shoes Yeah, you can take an extra pair of shoes to wear around camp. I just take out my inserts for comfy camp shoes. (some people do use camp shoes for creek crossings, but I haven't had to ford many creeks yet)
Nido Milk I really love Nestle Nido Milk. It's my super-ingredient, I add it to coffee and the Knorr Pasta Sides that are my staple dinners. It comes in 1 pound cans, and it's a bit hard to find in a supermarket--usually its in the Hispanic section, since it's a Mexican product.
Cell phone service is fairly available: Despite warnings that there's no coverage, I was able to get cell phone signal from my carrier (AT&T) along much of the PCT at least once a day, even in supposedly dead zones like section F and Mission Creek north of I-10. The PCT goes along a lot of crests and ridgelines, and you can see major roads often in the valleys and plains below you. One place where there's no cell service or wi-fi is Kennedy Meadows... there is a pay phone, though, so get a calling card set up before you head on the PCT, or buy one at the KM store.
Aren't you afraid of ______: Almost everyone will wonder how you're dealing with some bad nasty: rattlesnakes, bears, ticks, snow, whatever. The Internet (and the general climate of fear that's been promoted since 9/11) has made people think the world's a dangerous nasty place; it's not. The world is a wonderful place if you know how to deal with situations you might encounter. When people ask you how you're dealing with a nasty, it's not so much about what you're doing about it but more an expression of their concern and fear of something dangerous and unknown. Reassure them, don't go into too many details, which might freak them out even more (people are especially weirded out about rattlesnakes!)
That's it for now. I've compiled a little list of "Mental Lessons Learned" and will post that at some future date, once I've mulled it all over.