Whatever your approach, if you use some common sense and apply yourself, you can make significant quantities of money in the game. By managing your cashflow, conserving and budgeting where you can, and investing wisely in those activities that make you money, you can become financially solvent relatively early in your career, and remain comfortably well-off (while still buying good gear) at level 80. Good luck!

This is a risky way to make money, and not recommended. Tell a player that if he beats you in a duel you will give him 10 gold, but if you beat him he has to give you 5 gold. This can be very effective if you are skilled in PvP and make the bet with a trustworthy person, or friends. It is a very risky strategy, as you may lose gold, or the other player won't cough up the money anyway. You will also get a bad reputation if you don't cough up the money in the case of defeat.
The main tool for any serious gold maker is TradeSkillMaster. It is an addon suite with a desktop application that downloads price data and allows you to create rules for easy crafting, mailing, shopping and posting your items on the auction house. It has a premium service that includes e-mail notifications for great deals and importing great deals as a shopping scan.

The Horde will now control most of Kalimdor, and the Alliance most of the Eastern Kingdoms. For a low-level character the quests and storylines won't change, but for high-level players many zones will see changes via phasing. Teldrassil is burned and Undercity is in ruins as the story progresses by phasing. At max level Arathi Highlands and Darkshore are phased to be updated to reflect their status as locations for Warfronts.
Currently, it is believed that the War Mode rewards will change depending on which faction is more heavily prevalent with War Mode activated. The Horde have typically had more participating in War Mode, so the reward has been increased for the Alliance to incentivize more participation in War Mode. These rewards could potentially be increased to both the Horde and Alliance to incentivize both factions to higher amounts of War Mode participation.
Soloing an instance can be all the more profitable if your character is an enchanter. During any solo instance run, you'll end up with some items which can be sold or traded, and some that are bind-on-pickup. Non-enchanters can only sell these soulbound items to a vendor, but an enchanter can disenchant the bind-on-pickup rare items, and then sell the shard/dust/essence instead of just selling the blue item to a vendor. (A side benefit of selling enchanting materials is that they do not require a deposit to list in the auction house, allowing you to list endlessly until the item sells.)
You might be thinking that you don’t need a designated gold making character. I certainly didn’t think so as i used my Paladin for countless hours of gold making (Paladins are one of the slowest classes in the game). But then I decided to try to make a Fury Warrior with 170% base movement speed. Boy did that make a different, I run dungeons several times faster than the Paladin, hence making 3 or 4 times more gold per hour. When making a gold farming character, these are the most important points to remember.
If these tips are not up your alley, feel free to play the auction house as early as you have enough to buy one cheap stack of peacebloom. These low level herbs are fantastic sources of early income with little risk since everyone needs to level professions. Alchemists especially are popular every expansion because of the need for those high level trinkets that soar above even heroic drops. As a result, that peacebloom you bought for 10 silver now can easily sell during peak hours for well over a gold! This is a minimum of a 1000% profit! While 1 gold may not seem much, when you are selling 10 stacks at a time, those few hundred gold can go very fast and get you into the greater profit items. However, knowing prices on peacebloom and other lower level mats can prove difficult. This is where Auctionator finally comes in! Run a scan overnight on all your auction characters. You can now see whether or not a posted item is worth buying because of percentages presented next to the list. The major lesson to take out of this is to scan daily and see which items fluctuate greatly, as those are your rewarding items! Items that jump from 10s to 3g depending on time of day or uninformed buyers are a goldmine waiting to be taken advantage of. You can buy low and sell high, succeeding in the World of Warcraft stock market!
-Global Cooldown- Almost all spells are now on the global cooldown. This has slowed gameplay down quite a bit and you won't get to use the full potential of your spells cooldowns. For example, you cast a spell that increases your damage for 15 seconds, after the global cooldown and you're able to cast again, you now only have 13.5 seconds to make use of the remaining time. There are far too many spells on the global cooldown that shouldn't be.
Learned this today: posted a comment, came back later to see if there was any feedback, reloaded the page: the page posted a copy of my comment. That was not what I wanted. I just wanted to check if my comment was posted and if there were some responses. I did not want to post a copy of my comment from 5 hours ago. And, a humble guess, I think the majority of the users are not expecting such behavior either.

Destructions Warlocks have also seen quite a few changes at the beginning of Battle for Azeroth. As they currently stand, they are a fairly safe pick for most types of encounters. While overall their damage output is average, their sustained damage abilities make them incredibly stable and adaptable in both single and multi-target encounters. They also have the lowest ramp up time of any Warlock spec, meaning they will be good to go from the start of a fight. They also feature highly customizable talent trees which produces a more flexible gameplay that can be shaped on a per-encounter basis.
If you can answer all of those questions with yes, then you are in a position to make a lot of gold! You can continue doing every step to get to the gold cap as quickly as possible. The security achieved through this can buy you virtually anything you desire in the game, including achievements that would otherwise be impossible on your own, which leads us to the final gold making tip - Selling achievements. If you are the leader or officer in a guild, you can take good acquaintances on your raids with you for achievements like finishing ICC or any other hard raid achievements that your guild finds easy and manageable. I have seen achievements go for 20k+ if you find the right client! This is very situational, however, and is by no means necessary to hit the gold cap, it just helps!
Good question. Me personally, when I use a new strat from somebody else, I always read thru the strat, and in the case I really need to level some pet, I then (likely) exclude strats that are mentioning things like “RNG”, “risk”, etc. But: I’m always happy (when using a new strat) when I see some detailed infos, so that I can estimate what is going to happen. But YMMV.