My second least-favorite part: leveling ranges. Zones are divided into leveling ranges; some are for levels 10-60, others for levels 58-80, and so on. On the surface, that appears to make sense; while there are odd moments where you're presented with the content from two expansions at once, it does mean that you're more or less going through content in order, at least by expansion if not by level.
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Auto looting a mob will increase leveling speed for the expansion. to enable it = Esc, Interface, Controls, Enable Auto Loot. I'm including this because sometimes the simple things are missed. I, sadly, went 3/4 of the way through WoD not knowing that hitting the space bar for my mission tables is much MUCH faster than waiting it out. (i never claimed to be smart OKAY) =P
In that expansion, NPC followers could get an ability called “treasure hunter” that doubled any gold rewards they earned from a quest. And “treasure hunter” perks stacked, so it was possible to get a few thousand gold per day, per garrison. Many casual players who had never had significant amounts of money before earned hundreds of thousands of gold during Warlords of Draenor. Players could sock away millions, since each character could earn roughly the same amount of gold from their garrisons, and you can have as many as 10 characters on a server.
Gathering nodes need to be fixed. Herbalism and mining give small amounts of experience as you level, mostly rewarding you for going out of your way to gather nodes. A change a while back makes them scale naturally with your skill level, so that you can mine or herb anything, anywhere, just getting varying amounts of usable fragments or whole items depending on your skill.
C C'Thun Alliance C'Thun Horde Chamber of Aspects Alliance Chamber of Aspects Horde Chants éternels Alliance Chants éternels Horde Cho'gall Alliance Cho'gall Horde Chromaggus Alliance Chromaggus Horde Colinas Pardas Alliance Colinas Pardas Horde Confrérie du Thorium Alliance Confrérie du Thorium Horde Conseil des Ombres Alliance Conseil des Ombres Horde Crushridge Alliance Crushridge Horde Culte de la Rive noire Alliance Culte de la Rive noire Horde

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.
101+ At this point you'll start taking a penalty on quest/bonus objective experience for every level past 100. Treasures, however, remain worth their full value all the way through level 105, at which point they'll be worth something like 15% less, and then another 15% more when you ding 106. I recommend that you stop questing/gathering entirely, and collect all the treasures you can stomach, only avoiding any annoying to reach ones inside caves or behind elites/rares(where scaling does bizarro things).
Special note: At 110 it's almost certainly worthwhile to go and immediately get your Heart of Azeroth and first piece of Azerite gear from the BfA opening quest. It doesn't take long and provides pretty high power levels. I'd then return to Legion quests until 111 or even 112, since the power of these items will increase your kill speed significantly over the scaled enemies of BfA content.

From my experience on the Beta as an enchanter/tailor, scrap every trinket (and maybe rings). Trinkets seem to always give expulsom and it's needed in the higher enchants. Scrap any cloth green drops for the extra cloth, but other gear and blues and purples disenchant for the mats. The scrapper seems bad at the return on some items. I'd scrap old Azerite armor and get some cloth and a bit of thread.
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