Although the Battle Pet Trainer will only offer to teach you your race-specific companion, it is possible to add all of these pets to your collection. You can either find them in your faction’s auction house or you can create a character of the race whose pet you would like to learn. Using your new character, you can seek out any battle pet trainer in major cities. After you learn the pet, you can delete the character; the pet you learned will not be removed from your collection.

Most of the time you spend leveling will involve questing and slaying monsters, but there’s also a lot of travel. Travel earns you little experience (you do gain a bit for discovering new areas), so it’s wise to keep travel to a minimum. The new level scaling system, which scales zones to your level within a preset range, helps with that. You can choose what zones you want to experience and stick with them until you finish their quests.
Valid pieces for Azerite empowerment are available for the chest, shoulder, and head slots of all classes. This equipment has multiple tiers of that can be unlocked, represented by a series of concentric wheels with icons representing individual powers; as individual powers are selected, they rotate into slots at the top of the interface, activating the selected benefit and locking out the others unless the player pays to reset their decision. Outer rings offer multiple choices, some based around the character's class and specification, others around the zone or circumstances in which the gear was acquired. The innermost circle offers no such options, instead being a boost to the level of the item itself, and thus providing a flat all-around benefit.
A common mistake of new players is to upgrade their gear at every opportunity, paying for a new piece even if it will only add one or two new stat points over an existing item. Likewise, investing in headgear, neckwear, trinkets, and rings at the earliest available levels can also consume valuable cash. While it might seem foolish to leave an available slot empty, you will eventually find something to fill it. Blizzard will see to it via the quest rewards you'll get along the way. In the mean time, the 1 or more you save will serve you well if you invest it wisely. The bottom line is that one can easily level all the way to the maximum relying on just quest/drop greens. The gear you get from regular questing can help you perform well in dungeons, which gets you even better equipment.
Step-by-step class guides are on the way!  The 1-12 Mulgore Guide is the first guide to get all the individual class steps.  At the top of the guide, simply select which class you are playing and the page will dynamically update all the steps in the guide for that class (both text and images).  The rest of the guides will be slowly updated overtime to include all the class steps, but you can see how it's going to work with the 1-12 Mulgore.  I want to thank crazyK and his Placeholderguild for helping me out with the individual class content.  They are allowing me to get the 1-60 Alliance guide done while also getting all the class steps done at the same time, so everything can be ready for Classic launch (hopefully).

Sometimes you can make money by crafting items with ingredients supplied by other players who give you a tip to make the item. This is not necessarily a reliable source at low levels, but it can be a good supplemental income source at higher levels, particularly if you have good recipes. And if you can charge for the customer using your materials (as opposed to materials supplied by him/her), you can mark those up.

While leveling, try to make use of the new Battle of Azeroth experience gem, Insightful Rubellite, which gives you +5% experience. Equipping one of these requires a socket in your gear, so try to hold on to a piece of Legion gear with a socket or acquire one of the Legion Legendary rings since every class has one. Each of the rings includes a socket. You can acquire one of these rings rather easily by doing World Quests in Legion zones and acquiring 1,000 Wakening Essences that can be used to purchase a legendary ring in the Legion version of Dalaran.
ifgte(ItemQuality, 1, minprice * ifgt(minprice, P6V, P6P, ifgt(minprice, P5V, (minprice - P5V) * (P6P - P5P) / (P6V - P5V) + P5P, ifgt(minprice, P4V, (minprice - P4V) * (P5P - P4P) / (P5V - P4V) + P4P, ifgt(minprice, P3V, (minprice - P3V) * (P4P - P3P) / (P4V - P3V) + P3P, ifgt(minprice, P2V, (minprice - P2V) * (P3P - P2P) / (P3V - P2V) + P2P, ifgt(minprice, P1V, (minprice - P1V) * (P2P - P1P) / (P2V - P1V) + P1P, 0)))))) / 100)

Engineering is a crafting profession that primarily revolves around fun recipes. The gold-making potential from engineering is limited in terms of Legion recipes. The Skullblasters can be obliterated for profit. Engineering has a lot of profitable old world recipes, primarily mounts and various unique effect items and toys. This profession is best relegated to an alt unless you love the lore-aspect or have other sentimental reasons to keep it on your main.
Incursions are a new world content activity that are unlocked when one character has unlocked World Quests. This feature is unlocked account-wide meaning that all characters on that account can access Incursions even without being Level 120. This provides for a lucrative experience acquisition method that is available in a similar pattern to what Legion Invasions offered with nearly an entire level earned by completing an Incursion series which involves four World Quests and one mini-scenario at the end. These also grant item level 370 weapons and Azerite armor, so they should be done any time they are up. Incursions follow a similar schedule to Invasions and are available for 20 hours once they are initiated.
-Island Expeditions- Island expeditions was one of the new features I was looking forward to but Blizzard no longer makes games that are ready when they are ready but rather makes games ready when the deadline comes. Thus, many of the new features are completely stripped down from what was expected and it's literally just a small scenario you enter with two other players to continue to grind out your Azerite neck piece.
ifgte(ItemQuality, 1, minprice * ifgt(minprice, 250000g, 80, ifgt(minprice, 100000g, (minprice - 100000g) * (80 - 70) / (250000g - 100000g) + 70, ifgt(minprice, 50000g, (minprice - 50000g) * (70 - 60) / (100000g - 50000g) + 60, ifgt(minprice, 10000g, (minprice - 10000g) * (60 - 50) / (50000g - 10000g) + 50, ifgt(minprice, 5000g, (minprice - 5000g) * (50 - 30) / (10000g - 5000g) + 30, ifgt(minprice, 1000g, (minprice - 1000g) * (30 - 10) / (5000g - 1000g) + 10, 0)))))) / 100)
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.