There's a ton of resources out there, so rather then write a mammoth wall-o-text, I'm going to make this as short as possible while linking all over the place so you can get as in-depth as you want.
Feral Druid Things
1. Ger the Glyph of Travel as soon as you can find it on the AH, it makes getting around so much easier. Ditto Glyph of Savagery.
2. As soon as you get the Rake perk, you'll want to open with that from stealth, instead of Shred. Of course, if you're in ubergear, you can skip the stealth part altogether and just demolish things, but that goes away as you level.
3. Spec SOTF for leveling, but use Incarnation for dungeons. It's a surprisingly good talent. Force of Nature is unsurprisingly terrible.
Links:
Pawkets' guide for level 100 with new WoD discussion thread.
Leveling Quickly
1. Stack some combination of Isle of Thunder/Shado-Pan/Klaxxi/Timeless Isle quests. Log in at Isle, port to Shado-Pan, hearth or fly to Klaxxi, trinket port to Timeless Isle, guild cloak port to SW, Mage tower port to Blasted Lands. If starting at 12AM, may want to only save 20-22, start questing immediately, and hearth out/back once you get garrison port.
2. Consumable up - might as well use them. Food, flask, DPS potions for rares/overpulls, etc. If going all-out, get speed (Darkwater) potions, slowfall potions for shortcuts, gems to gem gear as you get it, etc. Cracked Talisman is also very useful.
3. Buy all 3 guild battle standards. They buff XP gain from monsters and treasures by 15%/10%/5%. 10 minute CD per banner, so you should be able to drop one for most treasures you find.
4. Or, if you want, totally ignore everything in this section and level at your own speed! That's perfectly cool too!
Links:
Leveling Preparation Guide. Skullflower's Guide is excellent. If you only read one thing, read this.
Horde Speed-Leveling Guide. Step-by-step questing, Hordeside.
Alliance Speed-Leveling Guide.Step-by-step video quests and treasures. Recommends spending garrison resources on XP potions, which I wouldn't recommend.
Waypoints to all WoD treasure chests. Treasures are very prevalent in WoD - there are 20-40 in each zone. They are like Timeless Isle treasures; they're phased so everyone can pick them up (once). Treasures give slightly less XP then completing a quest.
Professions And Garrisons
1. You're steered to your Garrison immediately after finishing the introductory Tanaan quests. Once you finish the intro garrison quests, you'll have a L1 Garrison with an open small plot and a Barracks-filled large plot. After finishing the intro zone (Shadowmoon/Frostfire), you'll unlock a L2 Garrison, which opens an extra small and medium plot. L3 isn't available until 100 and adds an additional plot of each size, for a final total of 3 small, two medium, and two large. You'll also pick up some extra buildings along the way that everyone gets: the mine, the herb garden, the fishing shack, and the pet menagerie.
2. Gathering professions are largely unaffected by Garrisons. Gathering is super easy in Draenor as you can gather from any node (or skin) regardless of skill, you'll just get less from it.
3. Small building are mainly for crafting. Each crafting profession has an accompanying small building that can build most (not all) of Each profession also has a Unique Resource (I'll use engineering's, Gearspring Parts, as an example) that must be generated in order to build most of the new cool things. Stay with me here, this gets a little complicated.
* If you have BOTH the crafting building and matching profession, you can get 16 of your Unique Crafting Resource per day; 10 from the profession, 6 from the building.
* If you have the profession, but not the building, things are mostly the same. You only get 10 Resources per day, and you have to go to Ashran instead of your garrison to learn new recipes, but that's it.
* If you have just the building, you can do some things with the building, but it's limited. You'll only get 6 Resources per day and can spend the Resources for the base-level crafts, but won't be able to buy the upgrades or unique items.
Other than the crafting buildings, there's also the Storehouse for extra work orders and garrison bank access (meh) and the Salvage Yard for extra rewards from follower missions.
4. Medium buildings give you stuff. The Barn gives Savage Blood (needed for ALL epic crafts), the Inn gives you daily dungeon quests and more followers, the Lumber Mill lets you harvest Timber which turns into extra Garrison Resources, and the Trading Post lets you trade reagents for Garrison Resources (or vice versa). There's also a PvP building in there for some reason.
5. Large buildings offer buffs. You start with a Barracks for free, which buffs your followers and lets you make certain followers bodyguards, who fight with you in the wild. There's also the Bunker, which buffs quest rewards, can upgrade followers, and gives you free bonus rolls; the Stables, which increases mount speed and prevents being dazed; the Mage Tower, which lets you port around Draenor; and the Gearworks, which gives you a different fun toy/special ability to use every day.
6. My picks: I've changed my mind around a few times, but I've finally settled on these starting choices for my main, who is Alch/Engi.
* Small: Salvage Yard, Enchanting, Inscription. I like the follower minigame, so Salvage Yard is a must-take. I'm not building the Alchemy building because the Alch unique resource is only used for making a trinket and super-flasks; my profession should generate more than enough mats for that. I'm swapping in the Enchanter's building so I can disenchant quest greens. Inscription over Engineering is a tough choice; I will likely start with Inscription just to generate cards for a Darkmoon trinket, then switch it to Engineering later.
* Medium: Trading Post, Inn. Not a PvPer, so the PvP building is out (should've been a building that everyone gets, really). I went back and forth on Lumber Mill or Trading Post for a long time; both will generate you Garrison Resources, but Trading Post is ultimately more flexible and doesn't require you to go harvesting. Finally, Inn wins over the Barn because I'll be running a lot of dungeons at 100, though my alt will have a Barn to sell the Bloods.
* Large: Barracks, Bunker. Glyph of Travel means I'm not too concerned with the Stables, I think Engineering will give me enough toys to get around fast that I don't need the Mage Tower, and the Gearworks looks more like a "fun for alts" thing than anything else.
Links:
A garrison infographic by Ask Mr. Robot.
Grumpyelf's collected Professions posts. LOTS of info in here.
A garrison addon.
Things To Do At 100
1. Gear up! Questing should've gotten you up to around item level 610. Heroic dungeons drop ilevel 630 gear, and CM dungeons drop ilvl 640.
2. Start farming Apexis Crystals. These primarily come from a daily quest in your garrison. You need ~5000 Crystals as part of the legendary questline, and lots more can be used for gear.
Links:
A guide to gearing up at 100 by Wowhead.
Legendary quest guide by Wowhead.