Elemental items (Primals, Eternals, etc.) can be a good source of money, because they are always in demand on the AH. See which mobs you will most benefit from farming, then set out for a few hours. In the process you will also most likely collect significant vendor trash, and may get other profitable item drops as well. Note, however, that older elemental drops usually lose profitability compared to newer ones, i.e. Primal Water sold well to level 70 players in BC, but sells far less well to level 80 players in WotLK, because level 80 gear requires Eternal this'n'that.
For the duration of the fight, creatures in the immediate area will not be visible to you (but they may still attack you if they wander too close). Keep in mind that other players will still be able to see you and attack you if you are eligible for player vs. player (PVP). Other players will also be able to view your pet battle in real time, including the pets involved as well as their health as the match progresses.
Repetitive daily quests are a legitimate method of generating significant cashflow. Players who spend several hours a day doing daily quests can often generate 100 per hour. Many players have funded the purchase of their elite flying mounts solely through doing daily quests. Another trick for higher level players is to do level 70 dailies as a level 75-77. If you have a hankering to get a Netherdrake, for instance, and you already have a fast flying mount (which is a pre-requisite for the drake), you will find your mid-70s an ideal time to go get that drake. Not only will the quests be a lot easier to do at level 75+, but the dailies will pay about 1200 as you level rep, and you'll get XP along the way to boot (albeit not as much as quests in Northrend.) So if you're looking for a break from the grind of leveling to 80, and want to kick back, spank some level 69s and make some decent money along the way, doing lower level dailies can be a fun way to make some extra cash.
Isle of Quel'Danas: Special mention. At lvl 70 you can start doing the dailies here. Despite not being able to fly, the quest density is VERY high. I recommend hitting this every reset if you spend more than 24 hours REAL time(not /played)in the 70-80 level range. In fact, if you're doing a monk and only logging in once each day anyway, IQD WILL be your best exp/h for this level range.
Similarly, when earning by volume, do not overload the AH with your items. Basic supply and demand: too much supply will make your wares too common and unwanted. Furthermore, with great demand and a cheaper price, you may end up starting a price war with your competitors, with them actively trying to undercut and outdo you. Moderate the amount of items you're selling on the AH to small batches, refilling them only when sold out.
Making gold is all about finding the balance that works best on your server between all the above methods. When you find that balance, repeat, repeat, repeat, until you get the results you want. Never make any rash decisions without first consulting the economy. If you do not think you can make a for sure profit, then do not do it! Change only when necessary, because your clients become accustomed to certain practices that keep them buying from you even if under cutters offer a slightly lower price. If the customer is always right, then show that to them and you will be much more profitable!
Sometimes that requires players to earn gear to give them greater powers that they haven’t yet unlocked. That sense of progression is at the center of what makes World of Warcraft great and so successful over the last 14 years. There should always be a balance between gaining gear and strength through lower-level content and taking on the hardest challenges the game has to offer. With Battle for Azeroth, Blizzard has missed the mark. Getting to elite status just requires grinding content that isn’t fun, instead of players demonstrating their skills.
The upcoming raid, Battle of Dazar’Alor, tackles this problem by having the Horde and Alliance have two raid stories — and the opposite faction will temporary flip sides for flashbacks that show the whole story. The Alliance storm the Zandalar capital and gain a massive upper hand in the war. From there, the writers will have to balance a compelling Alliance story with the rising threat of the Old Gods (and, of course, the ongoing Horde story.)