With that in mind, I decided to offer some suggestions on how to keep this game worth playing. The usual disclaimers apply; this is only my experience, I'm not God, your mileage may vary, blah blah blah. ;-)
Tip 1: RP servers are the best kind.
Although this isn't as true as it used to be, it's still largely true that preferably RP, but also to a lesser extent Normal servers, are where you've got the most chance of finding relatively stable adults to play this game with. Comparitively speaking, PvP servers are war zones, and just like such places in real life, tend to attract comparitively more aggressive, anarchic, violent, and juvenile people.
Don't get me wrong, here. WoW is the first game I've played where I've learned to genuinely love PvP. However, for the most part, that's battleground PvP. You can still have as much of that as you want on an RP or Normal server, whereas about the only three things you'll miss by not rolling PvP are, a) being spammed with duel requests by a Rogue ten levels above you as soon as you start a new toon, b) being serially drive-by speed ganked by Rogues while you're trying to quest, and c) hearing some 14 year old announce how potent his current stash of marijuana is on General Chat.
Tip 2: Don't roll Oceanic.
This is another one in the category of, "mistakes I've made, so you don't have to." I love my country; I just don't, in all honesty, love most of the people living here. ;-) Australians, I'm sorry to say, have a marked tendency to be aggressive, mind-bogglingly immature, excessively jocular people.
That's not to say that US servers don't have idiots, but it has overwhelmingly been my experience that on US servers, the idiot quotient is visibly lower, even on PvP servers. Also, although there are some notable, positive exceptions, people on US servers have tended to be radically more helpful, generous, and otherwise companionable, and I also remember a surprisingly insightful and genuinely enjoyable conversation I had on Demon Soul once, in Barrens General of all places. Although I've got a couple of friends on Thaurissan, in the public channels on Oceanic servers, intelligent conversation quite simply does not happen.
Aside from the above, PvE progression has a tendency to be poor, (which I normally wouldn't care about, except it makes buying high level enchants, crafteds, and gems a lot more difficult) and for those who enjoy playing the Alliance, at least a few of the servers are fairly heavily Horde-dominated as well. Avoidance, and rolling on the US servers, is strongly advised.
Tip 3: Define your own goals.
The attitude expressed on the forums is, "Raid, Arena, or die." Truthfully however, if you don't want to, there's no reason to be doing either of those two things. You can run Heroics and battlegrounds, and still get perfectly good loot from there, in addition to having a thoroughly enjoyable experience in many cases.
In addition, a strategy I developed not long ago was to look at the possible crafted items from a few of the professions now, and solo various old instances for the money to buy them, which, while intended for lower level groups, provide a good challenge to a single player at the cap. In this way, you're seeing content which may be unfamiliar if you're a newer player, you're getting a level of challenge which will more then keep you on your toes in at least some places, and you're also actually getting relevant loot in the end through the accumulation of money. Farming some of the old instances can be extremely lucrative, as well as an enjoyable activity, as I have shown.
Another mini-game within WoW can be speculation on the Auction House. Download Auctioneer if you're so inclined, and go and sit on the forums of that addon's site. You can soak up loads of knowledge about the in-game economy from people who proverbially speaking have very good lobes for business, many of whom work on Wall Street as their day job.
Build an army of servitor alts which you can use for gathering from all over the virtual environment; you'll end up making buckets of money, and it will keep you occupied for a long while. The other added bonus here is, if you think you're burnt out on this game already, believe me when I say it gets better if you've got an appropriate amount of coinage. You could then buy an epic flying mount, or offer loans to people who want to buy their own, with interest. ;-)
The Arena and raids are what the proverbial cool kids do. You don't have to be one of them in order to have fun, though, and it's very possible that you'll actually have more fun if you're not.
Tip 4: Stay off the treadmill.
I've seen a lot of people in this game who treat it as a race. The moment a new expansion comes out, they have to be the first to reach the new cap, and to do it in under two weeks. Then they have to have the "world first kill," of whichever new primary raid boss is in existence. They have to be the first to get the new tier set of armor, etc etc etc.
These same people are the ones who write "I quit," posts in the General forum less than a month later. They tear through content as fast as they possibly can, in truth seeing hardly any of it, get bitter and bored, and hit burnout.
It took me more than a year to reach 70 with this Hunter, and I can truthfully say that if I could do it all over again, I'd probably take close to twice as long. This is a huge game. There is a lot to see, and a lot to do, and you won't experience it by doing by the bare minimum necessary to level up.
Roll a Protection Paladin/Warrior, Survival Hunter, or Druid.
Do all the quests. I did every last one in Zangarmarsh; I love that place.
Be happy with one level a day, or even one every few days.
Follow every path that appears in front of you, just to see where it goes.
Give yourself a good amount of time in the battlegrounds at the end of every bracket. Explore every nook and cranny you feel like in every zone you go into.
Smell the roses.
Have a place in the game where you do the virtual equivalent of going jogging. (Although real exercise is more important, of course) For me that was the Southern Gold Road at 4 in the morning, just listening to the night sounds; or Thousand Needles at dawn.
WoW is a true virtual world. Most are so worried about their e-peen that they never give themselves the opportunity to see it as such. That leads me to my next point.
Tip 5: Do not EVER let your game be about e-peen.
If this game ever becomes a source of self-esteem or ego gratification for you, it's likely time to stop playing. There are far too many people in this game who have as their sole motivation, a burning, never-fulfilled need to view themselves as superior to as many other people playing as possible, and they will invent whatever arbitrary, totally subjective criteria that they can for that purpose. Elitism is a more chronic problem in World of Warcraft than any other online game I've ever seen.
Don't be an elitist, and don't ever make a need to keep up with the Jones' a reason for updating your gear. That way leads to bitterness, insecurity, unhappiness, and burnout. Being elitist also doesn't improve the experience for your fellow players, either, and has a tendency to encourage them to dislike you; you only need to visit the official Hunter forum to learn that. There's more elitism there than in any of the other class forums associated with this game.
If you think you're progressing in terms of developing your abilities, a certain quiet sense of accomplishment is fine, but don't go overboard. The primary thing to keep in mind with regards to elitism is that no matter how good you think you are, in 99% of cases, there's always a bigger fish.
This is something I need to remember more myself, but in reality, the only person we should ever be competing with in this game is ourselves.
Tip 6: Find the class and spec that is in tune with who you really are.
I begin to suspect that upwards of 90% of people that I come across in this game aren't truly playing the right class for them, but ended up in the wrong one due to any number of extenuating circumstances, (peer pressure among them) and although they're not really happy, just struggle along.
Don't do this. If you want to be able to continue enjoying WoW for a long time, it's vitally important that you ask yourself Mr. T's question, "What's your game?" and then make sure you find out. Try and get one of every class in the game up to level 30 or so, maybe level 40. Some of them you'll probably hate right from the start, and be able to tell that they're not for you, and that's fine. However, with some of them, it takes time for the class to really grow into its' own. The Hunter doesn't get Feign Death until 30, and Misdirection until 70, and more than anything else, those two abilities are really our bread and butter.
Don't listen to the flavour of the month spec monoculture that is upheld in the various class forums, either. The Hunter's current dominant spec is Beast Mastery, and pre-TBC, it was Marksmanship.
Back then, Survival had literally the same degree of stigma attached to it as homosexuality used to. Threads written by people wanting to know about Surv truthfully sounded like the halting, scared confessions of the bi-curious. Before The Burning Crusade, speccing Survival simply was not done, and woe betide you if you did it and made it known. In addition to the vitriol that used to be heaped upon me was an element of genuine amazement, that anyone could be brazen enough to violate such a fundamental taboo of civilised Hunter society. BM and Marks were the only two trees anyone spoke of; Survival wasn't mentioned even in whispers. Before the change to Expose Weakness in patch 2.1, it was as though it literally did not exist.
Then, after patch 2.1, everything changed. Suddenly, Survival was what the cool kids were doing. It still wasn't the dominant tree, but it started being seen in the rebel offspec position, similar to how BM was percieved pre-TBC. Alumatine materialised seemingly out of nowhere, despite claiming he'd been around since 2005. Bandet got Gladiator with it in season 2, and in general, people started realising the truth of what I'd been trying to say all along. Even history was rewritten, and I started seeing claims that using hybrid Marks/Surv had been entirely respectable pre-TBC, when I had the psychological scars to prove otherwise. Survival was finally no longer considered exclusively the talent spec of Joseph Merrick.
The point is, if you want a Destruction Warlock, a Balance Druid, a Ret Paladin, an Arcane Mage with Blacksmithing, or a Combat Dagger Rogue with Herbalism and Alchemy, go ahead and make one. It's your character, it's your $15, and it's going to be your enjoyment alone which decides if you keep paying said $15 and playing. If you're not enjoying your current class and spec, dump them, and find a combination that you do.
Tip 7: There's no school like the old school.
Although a lot of the TBC content is enjoyable, preference is to be given to pre-TBC wherever possible. It's better designed, more detailed, bigger, (in terms of the instances) more epic, was visibly designed by people who actually cared about what they were doing, and just overall more fun. Apologies to the company, but as far as I'm concerned, it's a fact.
The original Blizzard North are not the people still working on this game for the most part, and it shows. The most entertainment you will get from this game, therefore, is pre-60, while you're still doing content that they did produce. Realise that, and if you're going to do 5 mans or raids, opt for the old stuff first, and enjoy it for as long as you can before moving to the new material.
That's not to say that enjoyment can't be had in Outland; it definitely can. However, the visibility of the degree of difference in overall quality between one side of the Dark Portal and the other can be jarring. I considered pre-TBC 10 out of 10. TBC from me, gets an 8.
Tip 8: If you're going to guild, make sure it's with like-minded people.
If you don't want to be one of the e-peen set, then it follows that you don't want to guild with them either. There sadly are large numbers of guilds populated by jerks, so make sure yours isn't before you join them. Restrictions on talent spec in particular for the most part should not be accepted.
Tip 9: If you're going to pug, develop spider sense.
What I mean by this is, when you get into a pickup group, you'll often see warning signs being displayed in the early stages of a run by individuals who are likely to cause problems. If you can learn to identify these, they can give you the opportunity to spare yourself some headaches, and simply find another group.
Acronyms and mangled speech ("plz," "plox," "lol," "QQ moar,") are generally the single best indication that the person using them is juvenile. (At least mentally, if not always chronologically) Being asked for a run through of practically anything is also almost a guarantee that the person asking you is at least under 18, and usually under 15. Realise that if you say yes to such a request, what you're essentially doing is volunteering to engage in unpaid babysitting.
Someone who seems to be paying excessive attention to inspecting or looking up the Armory profiles of others usually isn't a person you want to associate with, either. If someone is posting LFG
Also be very wary in 5 mans of individuals who can't control threat appropriately, since they will almost certainly cause repeated wipes. This is more common in lower level instances, but if you start to notice a pattern developing, be prepared to leave the group.
Along the same lines, don't tolerate hyperactive tanking. If you have a tank (Paladins tend to primarily be guilty of this) who isn't willing to wait for you or the healer to regain mana after each pull if needed, and who seems to want to skip adds (in the Coilfang instances, especially) and charge ahead generally, that is a warning sign to either leave the group, or prepare for a large repair bill due to repeated wipes.
That's pretty much it, that I can think of. I'm sure there are more, but those are the main ways that I've managed to stick with the game for as long as I have, when other people are quitting all around me all the time. Probably the single biggest thing to remember is every so often, to simply take a week off and go outside. ;-) If you do that, the game will be a lot more fun again when you come back.