As you continue to push through end-game content and you raise your reputations with various groups, you unlock more quests that send you to the opposing faction's continent where you generally try to mess with them, gather intel on their movements, and, of course, kill a whole bunch of them. These quest lines are fun, but generally pretty short and don't actually propel you through much of the three opposing zones.
I highly recommend actually staying in the 20-60 range zones until you ding 62. The reason for this is that despite getting a slight penalty in experience for being over-level, the advantage of having flight will more than offset this. That, and WOTLK and TBC zones are the slowest part of the leveling process. Minimizing your time there as much as possible is worthwhile.
Try to gather up all quests for a dungeon before trying to queue up for it. Preferably pick up dungeon quests as soon as they are available to avoid getting them when you are over leveled. Dungeons themselves reward a good amount of experience due to the grouping of mobs, but the quests on top of that reward great experience and decent questing gear.
Gold in WoW has value based on the time it takes a player to earn it. The various methods of farming gold, such as growing herbs, yield maybe 20,000 gold per hour. That means at a price of 100,000 gold, a token represents about five hours of grinding, or offers a wage of $3 per hour. The idea of gold being worth a certain amount per hour is a useful way of framing this discussion, in fact.
Take breaks. Unless you're straight up no-lifing it over a weekend or something, this leveling process is going to take ~40 hours. But any time you do need to step away, log out. That tiny little bit of rested exp is insignificant...but you never know when something might come up and you'll have to leave for a longer period of time than you expected. Better to be logged out and safe(especially with War Mode on) than AFK waiting for a d/c. Plus, you'll need to stretch, eat, shower, and maybe sleep. XD
Most heirlooms only work in a limited level range in their default form and must be upgraded to work at higher levels. That costs gold, and you’ll need around 30,000 gold to outfit yourself with a fully upgraded set (counting only those that give you bonus experience). You may need to spend some time on a boosted character to acquire the gold you need to outfit another character with heirlooms, but it’s well worth the effort.
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.