So I bought it. I let Kotick take $15 from me every month. And I need help. I am a total noob at this whole WoW thing after putting it off for five years. Who plays this? Don't worry, I won't tell anyone. Any tips and stuff? What realm are you in? You know, all that fun stuff.

I have stopped my subscription in december, because I needed to take some rest.
My characters are on EU realm Shattered Halls, but don't expect any über 1337 pr0 equipment, I never had time for raids and such things.
As for some advices:
Unless you have someone to play with, go to PvE realm. At least there won't be any max lvl bored kid boosting his/her ego on one-shotting your low lvl char. Not that it will happen all the time, but it can happen anyways.
Learn to use the auction house (Auctioneer addon ftw!), you can earn substantial amount of cash there, if you sell the right goods for the right price.
If you will start on a realm alone, it is good to take two gathering professions and sell what you find in the auction house. For example I have earned nice money by selling copper and other metals.

I played this game before I understood the value of time and vitamin D.
It really doesn't take much effort to be a high-end raider or top the arena charts. Find a decent group of friends (it is best to find people who you know from outside WoW) and you are set. Beyond that, you'll only need time, patience, junk food, and a job that lets you go 2 weeks without showering.
General tips to become pro:
-Grind alone most of the way (quests are key)
-Make sure to take up collecting of some sort and use the AH to get money (collect crap as you level and sell it)
-Distribute your talents to promote faster leveling, and then respec once you hit the level cap

You'll get bored if you play alone.
I'm playing with a nice number of friends and it's the only thing that keeps me going. I like raiding, but get bored of it quite easily, so it's on and off.
I'd recommend picking a class that can tank while starting, this will get you easy in dungeon queues, then you can easily farm badges for heirlooms (level-scaling, account-bound items) if you want to level other toons.
Guess you'll be playing on US, but these are my babies:
Mains:
http://eu.wowarmory.com/character-sheet.xml?r=Defias+Brotherhood&n=Nanael
http://eu.wowarmory.com/character-sheet.xml?r=Defias+Brotherhood&n=Armereth
And currently raisin' myself a healer:
http://eu.wowarmory.com/character-sheet.xml?r=Defias+Brotherhood&n=Acadea

Giving it a few months to iron out all the issues if there are any (being Cryptic there must be loads).

Thats probably a good plan although there are less bugs than I anticipated

join a guild. i got bored after the first month but i had the most fun doing stuff with my guild.

I'm on EU/Argent Dawn since about when the game launched in Europe. If you visit there you may on rare occasions be able to locate a dwarven lady by the name of Sanni or one of my other characters.
Alliance:
Sanni
Maille
Adrinei
Meran
Horde:
Thurbaxa
Berdane
Mirthe
Playing alone can get a tad boring at times, trouble is my so-called friends play only on PvP realms and I require a better reason than companionship before I head over to gankland.

And yes I am going to play on US with friends. Frostwolf realm.

I played this for a while a few years back, it was quite fun but as with most MMOs I got to lvl 30 and got bored. May be due to the fact I didn't know anyone else playing it at the time and wasn't on enough to make friends in game as they would out level me pretty quickly.

Looks like Frostwolf is a PVP server which I dislike, so Kilrogg it is.

Play as a Paladin.

Definitely good to have a group of friends to run dungeons, etc. I stopped playing six+ months ago and probably won't re-subscribe until the next expansion. As mentioned it really isn't hard to get into raiding but it ultimately becomes boring when you take that step back and wonder why you're doing the same thing again and again considering the time it requires.
Don't be afraid to ask questions about playing a particular class/filing a certain role -- there's a mountain of information out there but it would be pretty daunting for someone entirely new to the game to take in all at once.
The best advice would be to take it slow and enjoy the leveling process. A lot of people feel a need to rush to max level to start farming gear but they miss the point of the game entirely. Level a little while questing then take a break to run the dungeons as you hit the appropriate level ranges. Enjoy the scenery, take it in, and practice playing your class in a group setting. It's fairly pointless to farm max level gear at this point since a new expansion is due in about four to six months and they are, inevitably, a gear reset.
But, again, WoW is only as good as the people you play it with -- if you get with a good group of friendly people who don't take the game seriously it's a great experience. If you're forces to run groups with random hostile idiots and/or people who insist on running graduate level math equations to analyze the best possible outcomes you're going to loathe the experience.
Druids are a great all around class because they can be tanks, healers, or DPS both with range/magic and melee. Of course each class has a different play style so it will just take a lot of trial and error to see which you prefer best. If you have any specific questions once you get going I'd be happy to give some more detailed tips.

It will happen all the time. You can't stay in Barrens forever, and once you start hitting up Tarren Mill or Stranglethorn, it's on.
I probably did the biggest dick move for ganking ever. I NEVER engaged anyone, regardless of level, while I was leveling up. I wanted to level fast, not dick around with PVP unless someone attacked me first or I was in the mood. If some guy came after me and ganked me, I would log out, log in with my lvl 80 hunter, then proceeded to kill 5 lowbies in that area for every 1 time I was killed. If I logged back in and got ganked, oh well, logging out and raping some more alliance.
A dick move but you can't say they didn't deserve it.