Common methods of power leveling include doing only those quests which are most efficient in terms of experience over time, and analyzing the quests in a given zone so as to do them in the most efficient order possible. Remember, the idea of power leveling is speed and efficiency--you may wish to obtain an addon that will show you how much experience per hour you are gaining to test your techniques. Additionally, ensure your character's talent build is crafted for maximum endurance. You want as little downtime (walking, drinking, eating, crafting, typing, etc.) as possible.
I just leveled this char in about 2 days played time with a few hours of it being afk in cities.What I did was run every single dungeon one time and do quests while waiting in queue.That way you don't get bored and the experience gain is great.Works particularly good between 60 and 90. WoD is a piece of cake if you just have flying and Legion is questing + doing the per zone dungeon for the 100k xp quest. 

I've found the best way to level alts is Pet Battling over by Halfhill in Pandaria. My Nightborne Priest I got to 90 that way (the rest was WoD Treasures, then regular leveling post 100), my Mag'har Shaman I'm at 61 with 16 hours or so played. Having a second monitor to zone out and watch Netflix or whatever helps. I think it's the fastest way to get to 90 personally. I really dislike the leveling changes so I just Pet Battle now.
Elemental: Lightning Lasso - Grips the target in lightning, stunning the target and dealing O2% of the target's maximum health in Nature damage over 5 sec. Can move while channeling. Enhancement: Ride the Lightning - If there are more than 2 enemies within 8 yards when you cast Stormstrike, you also cast a Chain Lightning on the target, dealing [ 50% of Spell Power ] Nature damage. Otherwise, you conjure bolts of lightning to up to 2 furthest enemies within 40 yards dealing [ 50% of Spell Power ] Nature damage. Restoration: Ancestral Gift - You become immune to Silence and Interrupt effects for 5 sec after using Spiritwalker's Grace. Warlock
Drustvar is far and away the hardest Alliance zone, which is exactly why you want to do it first. If you have legendary items, they’ll still be usable, and if you don’t, this zone will still be easier early on than it will be later. Drustvar is also extremely fast and will let you jump out ahead of your competition in other zones, which means fewer players around to take your quest objectives.