Battle for Azeroth’s War Mode puts you into PvP mode and grants you 10 percent extra experience. But since the two factions will mostly level in separate zones entirely, you should almost definitely have this on when you’re leveling. That said, if you start getting killed by random PvP players consistently, stop using it. Although 10 percent is nice, it’s not worth dying every few minutes for.
The zones in Battle for Azeroth are littered with treasures and rare spawns that give the same amount of XP as quests. With Zygor's Leveling guide these points of interest are displayed directly on your map and can be clicked at anytime to add them underneath your current guide step. The guide will then switch focus to the POI, direct you to its completion, and tell you how to complete it.
“The biggest struggle of overhauls like item scaling is being able to exhaustively test it,” he said. “You can’t expect any group of a few hundred people to go in and hit every piece of content that’s ever been developed over the past 15 years of World of Warcraft. That is difficult and challenging to do. What we did was listen to a lot of feedback from the PTR, what those changes looked like there. “The community is a great resource for helping us understand what we missed, and we were able to develop technology to be agile about fixing the problems very quickly in a live environment when we did come across them. We did have a few hiccups when we launched the patch in terms of scaling issues, but a lot of those were addressed rather quickly and that’s due to the technology we’ve developed to hot-fix our servers and almost anything in the game without down-time.”
Gold in World of Warcraft is a currency that is awarded in small quantities for completing quests and missions, defeating enemies, and selling unwanted items to vendors. It is used in the game to purchase things like armor repairs, crafting reagents and the use of flight paths that ferry players to various locations. It is also the currency of exchange on WoW’s auction house.
These two expansions are virtually identical in terms of exp/h. I personally favor Mount Hyjal, and think it's very slightly faster. But if you know Jade Forest well you can just as easily keep up there. Ultimately you'll end up doing both anyway, so it's mostly academic. Every time I've tested Valley of Four Winds or Deepholme, or any other zone in MOP/CATA's level range, they were worse exp/h. You should not even need to complete both zones to ding 91, so it's more important to just pick one and go.
I personally like it but I have healed for 11 years. This will actually be the first xpac where I actually main a DPS (UDK) ever in my history of WoW. The thing I actually really like about pally is they have an Azerite trait that gives the whole group a mini stampeding roar whenever you use golden pony. That is a great utility for a class to have. If I decide to not do UDK I will be doing HPal because it’s the one healer I have never mained.
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.
“Dugi’s guides are the greatest thing that has happened to me in my whole time playing WoW. I have almost all of them now and they are so helpful and easy to use. It couldn’t be simpler to install them and start using them straight away. The waypoint arrows are spot on and each step of every guide is detailed with everything you need to know. They really are perfect and i have recommended them to all of my friends in-game.

Special mention is the Darkmoon Faire Top Hat and WHEE! buff. While not always available due to the DMF being inaccessible most of the month, if you happen to be leveling when the DMF is running, it might be worth your time to go and get these. AFAIK they do stack with heirlooms, although I have not personally tested it. Fair warning: These buffs do NOT stack with each other, and the hats disappear after the DMF goes away later in the month(unless you only log in when the faire is running).

Bags: This SHOULD be a no-brainer. The cheap-o version are Netherweave bags, but if you have the gold I recommend you get the largest bags you can afford, since it means you won't have to stop to clean them out as often. In fact, if you have an excess of gold, it's probably not even worth your time to stop and loot mobs that aren't quest objectives. This seems like a small thing, but over the course of 100+ levels, all those clicks to loot add up.
Edit 20 It’s been a week since this post and a lot of people are still reaching out to me with questions which is fine. I have had a few different people reach out to me to help make YouTube videos based off this guide and more info in BFA which I’m more than willing to do. Whoever gets the videos up first I will link them here for you guys to enjoy.