Excess Potion of Accelerated Learning: Acquired in your Garrison (part of the Warlords of Draenor expansion), this gives you a 20-percent bonus to experience from killing monsters and finishing quests. It lasts one hour, but you can buy it multiple times and use it back-to-back. Alliance players buy it from Sergeant Crowler, horde players buy it from Sergeant Grimjaw. Does not work above level 99.
AddOns (sometimes called addons, add-ons, or mods) are collections of Lua/XML code that augment, modify, or replace World of Warcraft's default user interface. Addons vary greatly in scope and size — they may display information not presented at all by the default UI, add functionality to the default UI (e.g. additional buttons you can press to do things), modify the default UI's appearance (e.g. by changing colors or positions of UI elements) without changing its functionality, or even replace the default UI entirely.
As you're leveling, I generally recommend you just follow the natural flow of the progression through each zone. They're laid out fairly reasonably. But don't be afraid to hop around, especially if you're near a quest objective. You shouldn't actually need ALL of the zones listed to reach 62. Pick the ones you like best. It's much more important to simply be as focused as possible and flow from one quest to the next.
Some players even turn this into their profession by systematically "plundering" vendors in the game world and then selling the items on the auction house at a significant markup. The reason why this works (even for items which are on unlimited supply at vendors) is, that many players don't want to spend time traveling to specific vendors to get hold of a recipe or skill book. They would rather pay a slightly higher price at their local auction house. In some sense, they use the auction house as a "super market" or "convenience store". So it is completely reasonable and legitimate to be the supplier for this convenience store and make money out of it.
At Level 18, you unlock Freezing Trap which is a long-term crowd control for all Hunter specs. It places a trap on the ground that encases the first enemy (not bosses or most big encounter adds) to touch it in ice for 1 minute. The effect breaks on damage. The trap has a 30-second cooldown, and the trap will exist for 1 minute after placing it. This is useful when you are feeling overwhelmed by too many mobs, for temporarily taking out a powerful mob from the fight.
You’ll gradually gain access to new War Campaign quests while leveling up to 120, requiring you to establish footholds on Zandalar, send followers on missions at the mission table, complete Island Expeditions, and reach Friendly reputation with Order of Embers, Proudmoore Admiralty, and Storm’s Wake. After you’ve reached player level 120, new quests will unlock at specific reputation levels with 7th Legion.
The Hearthstone has a cooldown of 30 minutes, but there’s a guild perk called Hasty Hearth that shaves the time by half, giving you a strong incentive to join a guild. Yes, even if it’s some random guild that invites you without warning. It may feel odd to join people you don’t know, but if they have Hasty Hearth (and most guilds do), joining can save you a lot of legwork.
Mining is one of the three gathering professions in the game. You mine from ore deposits for all the various ores in the game. Your customers will be blacksmiths, engineers and jewelcrafters. You can make good gold per hour from tons of different routes both farming for legion ores and farming old world ores. I personally don’t farm, so I can’t tell you the best routes, but check out Oldbess guide on mining for some great spots.

Most classes in World of Warcraft start at first level, but Death Knights and Demon Hunters are exceptions. They start at level 55 and 98, respectively. This alone can shave a huge chunk of time from your leveling experience. Of course, it only works if you want to play a Death Knight or Demon Hunter, but they’re both solid classics that can dish out damage or tank in a group.

Unless Blizzard has some real story shake-ups and a phenomenally tuned raid on the horizon, I’m honestly expecting the sharpest player decrease to set in within the next few months. The expansion itself has some interesting ideas, but sticking to a World Quest grindfest is quickly becoming the norm, and the Island Expeditions aren’t exactly exciting.

Mythic+ has some similarity to raiding, but it’s designed for just five players, instead of the 10-to-30 that can make up a raid. This mode tasks players with clearing the game’s dungeons, but with specific changes that make them harder, scaling up until it’s impossible for groups to finish. Players receive a keystone in their inventory that assigns them their dungeon, one of the game’s 10, and gives the dungeon a level. This determines how difficult enemies are and what effects might make them harder. If the group completes the keystone in time, they get a new, higher-level stone; if they, don’t they get a lower-level stone.

Also get the Heirloom Mount. Being able to have basic riding speed from the beginning will save you a lot of time if you're starting from level 1. Allied races start at 20, so this is a non-issue for them. It's important to note that Pandaren can not use this mount until they finish their starting zone and pick a faction. Being Horde or Alliance is a requirement of the mount.
-Warfronts- I liked the idea of warfronts because it blends elements of Warcraft III with World of Warcraft, however, it's not a PvP battleground or instance, it's PvE so given time, it's a guaranteed win so many people are starting to AFK in the warfront. Beyond that, there is only one warfront to participate in right now. Also, when preparing for a warfront, Blizzard presents you with daily quests to help "aid" the warfront, however, your daily quest turn ins have no bases on the progression of warfront. The warfront will continue to advance at the same rate no matter if you do zero quests or everyone does all the quests.

I made some route changes to the Horde levels 43-44 sections.  I have swapped 44 Dustwallow Marsh with 44 Desolace (the entire sections). This allowed me to do Deadmire (at lvl 43 instead of 38) and then go stop at TB to turn in Deadmire + The Black Shield at the same time, then fly quickly to do the Desolace stuff.  Doing 44 Desolace is now mandatory because I think its faster with the new routes. This will also make the level 53 grind much shorter.  I think these were great changes.

Majority of world quests provide pretty bad rewards. Running for a wq that rewards 130 gold is a waste. Resources are not that necessary apart of some rare profit missions or buying the seal for them. Azerite for non-raiders or nonmythics is pretty much useless to farm since every patch will lower their requirement, and aside from few occasions it brings not much of a value. Not to mention that island expeditions are probably easier/faster with rng chance for tmog or pets. So the only main reason to farm them is the reputation. The most important is getting to exalted for recipes but for that there is no cache. The rest is pretty much not needed.

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Heirlooms. At the bare minimum you make sure all the armor pieces upgraded to 110, since this is the lion's share of your experience increase. Neck and Ring upgrades are secondary, but still important due to being able to enchant them. Trinkets can't be enchanted, but you'll want them at max as well, if only to save time by not having to worry about replacing them as you level.
The zone you start in isn't under your control, in as much as it's pre-selected for you based on your race. But for leveling purposes we want to make scaling work for us as much as possible. That means sticking to the lower level zones. Even though scaling will increase the level of the quests and mobs in those zones, the layout and design of them is built for a player with no mount. So you'll blaze through them and gain more exp/hour than higher level zones which assume you DO have a mount.
Tiragarde Sound and Stormsong Valley are both fairly similar zones, but Stormsong is a little longer, meaning that you might not even have to finish it to hit 120. Tiragarde also comes with a bit of a warning. There are plenty of side quests to do in the zone after you finish the story quests. Don’t do them. It’s not worth the time or the experience you’ll get.
Nearly all quests offer cash or items as a reward, and often both. While completing quests shouldn't be your main form of wealth generation, it is something you are going to do anyway. The key to making the most of quests is picking your reward items wisely. Don't always pick the item that most fits your class - if it isn't demonstrably better than your current item, instead go for whatever reward sells for the greatest amount to the vendor. You can select the in-game interface option to display it in the tooltip. In general, if you can't use a quest reward for your character, pick either a plate-armor or melee weapon as your reward--these tend to sell to vendors for more than other items.
Of course this is pure speculation, but who thought the token would be beneath 200.000 Gold again? But the only thing important for you is to calculate at what point you make profit by selling the tokens again. If you consider it, you should take the risk! Worst case scenario: You have a lot of battle.net balance to spend for Gametime, mounts, pets and boosts/services!