As late as possible. Early on, you’ll want to follow the missions in Battle for Azeroth right up until you get the option to send a follower on a two-hour long quest. As soon as you get there, stop doing the War Campaign missions. You can come back to them once you have reached something like 119 and a half and finish leveling with those if you want. If you don’t use these missions to cap off your leveling journey, then they’re the first thing you’ll want to do once you reach max level.
A: We chose to go with the subscription-based model instead of that approach. We've taken the approach that we want players to feel like it's a level playing field once they're in WoW. Outside resources don't play into it -- no gold buying, etc. We take a hard line stance against it. What you get out of microtransactions is kind of the same thing and I think our player base would feel betrayed by it. I think that's something else you have to decide on up-front instead of implementing later.
“We would prefer a targeted solution versus just applying a band-aid fix that could mask deeper issues that could cause problems down the line, but at some point it’s not fair to give you a degraded experience for the sake of that investigation, so we’ll likely go ahead with a blanket health reduction in the near future while we continue to investigate. Either way, the current state is not the game experience we intended, and it’s something we will fix.”
Level with a pet if you can because it will help keep you safe. If your pet is tanking all of the damage from the enemies you’re fighting, you won’t have to. The other reason is that pets are easier and cheaper to heal than you are. If you don’t have a pet, make sure you know how to use your defensive abilities. You can’t level quickly if you are dying all the time.
Congratulations on reaching Level 120! There are a myriad of new things to do. The first thing you should do is head to your faction hub ship where you have been doing your mission table quests and footholds to pick up and complete the quests necessary to unlock World Quests. World Quests will provide you an opportunity to grind reputation levels, acquire gear, and gather Azerite. There are tons of new things to do that we will cover in our Level 120 Battle Guide found here: Level 120 Battle Guide