The Broken Isles are unique among WoW continents in that you can progress through zones in any order you want. Once you have made it through the initial quests in Legion, you are free to move about four of the new zones — Val’sharah, Azsuna, Stormheim, and Highmountain — as you wish, with enemies, quests, and rewards scaling to your level. The fifth zone, Suramar, is mostly locked away until you’ve reached a certain point in the story.
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
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).
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