Fully rested experience (this is the blue color your experience bar takes instead of purple) grants 200% more experience per kill. Quest experience does not work the same as mob experience. Instead of just using the rested bonus, quest experience pushes the bar further upwards extending the rested bonus. Say if half your experience bar is blue. If you turn in 10 quests all at one the normal experience from them all could boost a character a full level. Unlike mobs where the experience gain will use up said bonus - the quests merely 'push' the bar further. Doing this could net you a level and still have the 200% bonus for mob kills applying to milk the rest bonus.
You should try and quest efficiently - pulling several mobs if you can handle it, using your burst cooldowns while questing to kill everything faster. Many people would think that a 10-minute cooldown like Bloodlust is useless in open world, but you can do a "kill-15-mobs" quest in like 30 seconds if you pull a lot and use it. A free quest every 10 minutes is not that bad.
Congratulations on reaching Level 120! Now that you have hit Level 120 we recommend looking at our Easy mode page and Talents section to learn how to play at max level. To get yourself prepared for the end-game content ahead, we strongly recommend this Battle for Azeroth Raiding Lexicon/Spreadsheet by Medivh. It is a gold trove of information that will help you when gearing up in Battle for Azeroth and more.
Another popular leveling guide is called “Booster”, which is also available for all races of Horde and Alliance. Similar to Zygor, Booster is an addon that you view inside the game, and it tells you exactly where to go and which quests to do every step of the way to level 120. The leveling path was created by professional gamers, and optimized to make your leveling as fast as possible. Booster also comes with free lifetime upgrades and updates, so you literally just have to pay once and use them forever, which is awesome. It’s created by a company called Dynasty Addons, that has been around for almost 10 years, and their guides and addons have always been updated in a timely manner for every expansion pack. It’s easy to see why this leveling guide is so popular.
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
Again, I play on Hoard side. I had an issue with the War Campaign guide. The guide suggests I pick up the “Wanted” posts at each outpost. I was not able to pick up these until I had finished unlocking all three outposts and the World Quests. I was able to proceed with some of the guide by manually double checking them to X, but the guide didn’t work quite right after that. I had to go back and pick up the next Outpost then it would be ok, until at the next location I needed to X the Wanted quests again.
The Horde 12-25 (Barrens + Stonetalon Mountains) guide has been rewritten and revamped. In addition, there has been numerous tweaks to the speedrun route to make things faster and easier to follow. Also, in case you haven't noticed I am now adding about 40% more info per step and redoing all the images. Unlike with my previous vanilla guides, I am now giving a brief explanation of where to go and what to do with each step along with any other helpful tips.
Something to keep in mind as well is that this will make enchanting materials more valuable, since it is likely most players will now simply scrap their boe greens instead of getting them disenchanted. Also redundant dungeon/raid gear can be scrapped rather than traded to the (guild) enchanter in the run. Less stuff gets disenchanted, meaning there will be less ecnhanting materials, meaning their value will rise. All the more reason to DE rather than scrap as an ecnhanter.