Some of this will be a straight copy and paste from the old guide. A lot of it has changed, re-read it. The majority of changes are after the Ta'naan Jungle part.

Preface:
This expansion includes the garrison. Many of us had hoped it wouldn't play a role in the end-game, but the opposite is true. The garrison is the focal point of the expansion, you can't just level to 100 and then begin doing garrison content. The most optimal way to level and prepare yourself to raid is to do every single thing this expansion has to offer while leveling. You will need to:

Complete all quests in every single area.
Kill every single vignette mob. There are often 30+ in each zone. Luckily they are similar to Timeless Isle, as in they show the skull on the mini-map and have a very short respawn timer..
Loot all zone hidden treasure.

Be ready for the 90-100 process to take 14+ hours.

0 - Preparation:
Drop your cooldown reduction trinket for something that grants a permanent primary stat.

Sorted in order of usefulness:
Weak Auras - VERY IMPORTANT
TomTom - VERY IMPORTANT
BoA weapons - Very important
250 DPS potions - Macro these to any ability you use mob to mob.
20 Flasks - Stat boost
20 Food Carts - I prefer these because they do not take 10 seconds to eat.
100 Healing potions - Useful in some areas. No longer shares a CD w/ DPS pots.
http://wod.wowhead.com/item=49633 - If you aren't a druid / paladin.
http://wod.wowhead.com/item=81354 - Allows you to walk on water, useful in some areas.


0.1 - Skip Cinematics & Use Quest Items:
This is somewhat risky as it is considered automation, and if blizzard really wanted they could find a way to ban you for it. But if you are trying to squeeze out all the possible time you can do the following:

1. Download AutoHotKey
2. Modify the AutoHotKey file in /user/documents to the following:

Skip cut scenes:
f2::
{
MouseGetPos, x_initial, y_initial
send {Escape}
sleep 25
MouseClick, left, 850, 549
MouseMove, %x_initial%, %y_initial%, 0
}
return

Use quest item: 
f3::
{
MouseGetPos, x_initial, y_initial
MouseClick, left, 1800, 230
MouseMove, %x_initial%, %y_initial%, 0
}
return

*Note, these only work on a 1920x1080 resolution.

0.2 - 11:55 PM:
We'll all be sitting right here until the expansion is activated.



When the expansion is activated one of two things will happen.

1. This will pop up on our screeen:

In which case you will just turn the quest into Archmage Khadgar, accept the next quest and skip (or watch the cinematic if you're Berg).


2. We will not receive that popup, and a quest will just be available from him:


In either case, because this area will be incredibly populated and it will be hard to right click him with 500 people on top of him:
Have "Interact with target" bound to something you can use:



Have Archmage Khadgar targeted the entire time.
Because there will probably be multiple hunters trolling people by changing their pets names to "Archmage" you may want to type his entire name.

/tar Archmage Khadgar

Then hit your interact key.

1 - Ta'naan Jungle:

This may be the most important part of leveling. If you are able to get ahead of the curve by doing this area fast you will not have to wait on quest mobs / item spawns. I strongly recommend going on beta and practicing this area a few times. The amount of time it should take if you are practiced is no more than 20 minutes, a small amount less if you group up with one other person who knows what they are doing and split up doing the quest objectives.

There will be a few quests here that will be particularly annoying if you are stuck in the bottleneck. Nothing you can do to help it except for getting ahead of the pack.

Here is a video of Tanaan done somewhat quickly:
https://www.youtube.com/watch?v=CjXmTBTaQtI

2 - All Of Draenor
Things got a lot more simple. Don't worry about anything besides the quests as you are leveling. However, do every single quest in each zone, complete the following:

http://www.wowhead.com/achievement=8671
http://www.wowhead.com/achievement=8924
http://www.wowhead.com/achievement=8919
http://www.wowhead.com/achievement=8926
http://www.wowhead.com/achievement=8928

Why?

Faction reputation for garrison followers.
Garrison resources.
Treasure maps for more garrison resources.

3 - Misc. Information to use while leveling
Majority of this information will all be copy and pasted from the other revision, all still useful. Read 'Obtaining Garrison Resources'.

The Garrison:
The initial quests in Frostfire Ridge will conclude with the construction of the garrison. Everything in the garrison is fueled by garrison resources. These resources are used to build new buildings, upgrade buildings, and send followers on missions. Garrison resources are going to be incredibly hard to find initially and they are very important. They are obtained from the following sources:

Obtained slowly, over time.
Obtained from vignette monsters on the first kill
Obtained from group quests and some important story quests.
Obtained from select follower missions.

You need 10500 garrison resources to upgrade your garrison to level 3, as well as every single building to level 3. However, not every building needs to be fully upgraded.

Obtaining Garrison Resources
This will be your direct focus for a few hours once you hit level 100. While leveling you only obtain garrison resources from select quests and a few bonus objectives. However, at level 100 you will go back into each zone to do the following:

Kill every single vignette mob one time.
Loot all zone treasure.

Each not level 100 vignette mob will grant garrison resources on the first kill. You will use a weak aura to find and kill these.
Most zone treasure grants garrison resources. You will buy the a treasure map from a vendor in Ashran which will mark every single treasure location on your map. This is only purchasable if you have the loremaster achievement.

Frostfire Ridge Zone Buff:
Every single zone in this expansion will have either a buff or an ability you can choose from. Frostfire Ridge is somewhat unique in that you unlock these buffs through "Shamanstones", which are scattered throughout the zone. However, the first Shamanstone you will encounter is tied to a quest and will give you the buff you should use throughout the zone. It gives you a 30% out of combat movement speed boost.

Other zones are different in that they will give you a GUI option between two different quest-lines and will both award different zone specific abilities that are quite good. I'll let you know which one to select in the respective zone guide.

Gorgrond Zone Buff:
Around 5 quests in you will reach your garrison outpost and have the option to choose between The Sparring Arena or The Lumber Yard. You should choose The Sparring Arena. This will give you the http://wod.wowhead.com/spell=164221 buff. While this buff is active you will essentially one shot all mobs. IT has around a 50% up-time. This will also give you the quest-line to the north of Gorgrond, and unlock the south area as bonus objectives.

Talador Zone Buff:
You will again have the choice between two buildings to construct for your outpost, each giving a different active ability. Unlike Gorgrond however, the choice is really up to you as to which to choose. Both are decent against named and boss mobs. Selecting one or the other will only affect the 3 quests directly following your decision, and then it is back to the main quest-line.

http://wod.wowhead.com/spell=162075 - http://wod.wowhead.com/spell=161768

Spires of Arak Zone Buff:
Around ~15 quests into the zone you will have the option to build two different buildings. The choices are between http://wod.wowhead.com/spell=168487 and http://wod.wowhead.com/spell=170108. The first gives you an ability which grants a 5 minute hearthstone in Spires of Arak and increases experience gain by 20%. The second summons a vendor every 10 minutes of which has a chance to sell you Garrison Resources. The first is likely useless, I would grab the second one and use the vendor on cooldown while both in the zone, and on cooldown as available while you are not gated by the resources.

Nagrand Zone Buff:
This is probably the easiest decision between two options you'll have made. You can choose between summoning a Siege Tank to fight for you on a 5 minute cooldown, or a mount that is usable/summon-able during combat and you are no longer dazed.

4 - Nagrand Complete & Level 100
Here is the priority chart for use once you complete Draenor. Each will be evaluated on in the following sections:

1. Return to your garrison, place the buildings you want. You will have a ton of quests to do. Go to Ashran, set your hearth. Buy the treasure maps. Send your current followers on missions.
2. Revisit each zone to kill Vignettes with the weak aura, and use the treasure maps to loot all treasure for garrison resources.
3. Obtain 8-10 level 100 garrison followers.
4. 5 Man Heroics
5. Group Apexis Crystal farming.

1 - Return to the garrison.
At this point you will probably only have enough resources to upgrade your garrison to level 2 and place a few buildings down.
Place the following:
Small: Salvage Yard - Required
Small: Optional
Medium: Lumber Mill - Required
Large: Barracks - Required

There are a ton of quests to do at this point. Pick them all up and get them out of the way. There is also a legendary quest that will send you back to Talador, start that chain before you do dungeons. You will get a 680 ring before stepping into any raid.

When you get the quest that brings you to Ashran, fly there. Set your hearth. There is a vendor here:

Buy the treasure maps. You should be able to buy all five if you completed the loremaster achievement. Now your map will look like this:


There are also reputation vendors all in the same building, find them, buy whatever follower contracts you have unlocked at this point.

2. Obtaining garrison resources from vignettes and treasures.
Now that you have all the treasure on your map, import this weak aura and enable TomTom: http://pastebin.com/abh0JXgb.

Go to whichever zone you wish to start in, make the weak aura show by hitting CTRL+F7. If it doesn't show type /reload.
You should see this:

As well as an arrow pointing to the nearest vignette:


Work your way through each zone. Kill each vignette and loot all the treasure. Getting each should grant a fuckton of resources.
Once done, return to your garrison and upgrade it to level 3. Place the following buildings:


Small: Salvage Yard Level 2 - Required
Small: Optional
Small: Optional
Medium: Barn Level 2 - Required
Medium: Lumber Mill Level 2 - Required
Large: Barracks Level 2 - Required
Large: Bunker Level 2 - Required


Again, send your followers on missions as soon as they become available. It is important to always keep them going on missions.

3. Obtaining Garrison followers.
You will need 10 level 100 followers all geared at around a 640 item level to be able to successfully complete garrison raid missions. Getting a head-start on this process should allow you to start getting gear once a week starting week 1 of heroic progression.

At this point you will have 2-3 level 100 followers, as well as a few 99s.

Wowhead already has a much better guide than I could write on obtaining these.

4 - Heroic Dungeons
This will take a lot longer than it previously has. Dungeon gear can roll Warforged, Socketed, and Tertiary stats, all independent of each other. You will want as much Warforged, Socketed gear as possible. Tertiary stats don't give any throughput but can still be useful. At some point it will become more efficient to start grinding Apexis Crystal epics.

5 - Apexis Crystals
Most of this shit will be figured out as we do it on live, it's impossible to really figure it out on beta. Apexis crystals are essentially the new valor points capped at 20,000, however they are fundamentally different. In your garrison, there is a daily quest that awards 800 of these. They are also obtained from killing a level 100 vignette mob on the first kill, as well as a chance to drop from any level 100 area mob. They can be used to buy the following gear:

Stage 1: Rare 630 Ilvl




Stage 2: Epic 645 Ilvl - Requires Highmaul Available




Stage 3: Epic 655 Ilvl - Requires Blackrock Foundry Available



Purchasing a stage 2, or stage 3 piece will require the previous piece. You must purchase 1 and 2 to get stage 3.

Basically, you will want to obtain all 630 ilvl rares before Highmaul comes out, and be capped at 20k for the release of Highmaul. Don't spend any of it until after we have cleared all 7 bosses and obtained loot. Then, upgrade whichever piece to stage 2 that is still an upgrade. Do the same thing with Foundry gear.

It's hard to tell how much farming we will have to do with how much time in-between raid releases there is.

6 - Crafting gear and other gear sources:
There is also crafted gear that is done in stages as well, I do not know much about it. Romo knows a little more about this, see this thread http://www.overture-guild.com/thread/8889/garrison-overview-mainly-concerning-professions

Max 3 pieces to be worn at a time.

There is 665 ilvl random world epic drops that you can probably purchase of the AH before any raid release.

There are three world bosses.. two will spawn once Highmaul is opened and one that spawns once Foundry is opened.

Theoretically we can be in the 645 ilvl range before any raid even opens. HWF dungeon gear is 636. MWF gear is 701.