Unless low quality items have some known quest use or are coveted by other players, you should try to sell it as soon as possible to create bag space. Always (or almost always, see above exceptions) keep things like cloth, leather, herbs, or large stacks of white/gray items over other loot when you have to decide what to keep when your bags get full. It might be worth your while to invest in larger bags (10-20 slot), especially if you know a tailor.
Patch 8.1.5 Hotfixes: March 26th Some early hotfixes today as we get more nerfs for the Zandalari regeneration racial, Paladins get less hasty, everyone gets 50% more conquest points in Rated BGs and Arenas until the 9th weekly Conquest Reward, Tiger's Peak is closed down as previously announced, in addition to the usual bug fixes for quests raids and achievements. World of Warcraft WoW Mar 26, 2019 at 17:10 by Starym
If you are not the leader of a high tier guild, do not worry because you can still make gold off of raids. This is the newly emerging GDKP runs that a respectable raider can put together (See why it is so important to keep a good reputation on your main toon?). Respectable raiders often take a few of their friends they can trust that have a lot of gear and bring random people along through the raid. Whenever a boss is killed, the items are auctioned for whatever base price you establish or more. You then split the money with your friends to keep everyone trying and happy, while you become richer without doing anything out of the ordinary. This seems like a perfect idea that can not fail, but it still has its risks. The tips below will help maximize the potential of the GDKP run.
Then 8.0 came along and turned everything on its head. Most of the techniques and shortcuts discovered, after 7.3.5 introduced scaling, were nerfed into oblivion. Many of the old techniques were confirmed by myself, first hand, to no longer work. I'm hoping that this thread can serve a similar purpose as the old thread, and gather as much data as possible on the fastest methods under the new system, and facilitate as many different perspectives and opinions on speed leveling with constructive discussion. I've just finished leveling to 110 under 8.1 with the exp curve.