Don't ask me to run you through an instance, only to log off when I'm halfway there, or even worse when I arrive. Especially if you do this with no kind of warning. (I mean, hey, I understand if something comes up and you have to go offline, like someone said "let's go out to dinner" or "if you don't get off the computer now, you're grounded for a month" but you could at least say something like "hey, I'm sorry, I gotta go").
Also, don't ask me to run you through an instance, only to say "nevermind" when I'm halfway there or when I arrive.
Don't agree to join a group if you know you're going to leave in five minutes.
Don't beg to be run through an instance. Ask nicely, or STFU.
Don't ask for someone to help you with a quest and then expect them to help you through the next ten. Ask them nicely if they mind helping some more, or GTFO.
Also, if you ask someone to "help" you with a quest, you should actually, I dunno, do something during the quest other than bark orders. That's not me "helping"; that's me "doing" the quest for you. And whether I'm "helping" or "doing", don't ever bark orders.
If you're in a guild, don't bitch about the lack of money in the guild bank for repairs, especially if you never contribute to the guild bank in the first place.
Don't try to force me to join your group just because you see I'm a level 80.
And if I do join your group, don't try to force me to be the tank. I am NOT a tank. At least not yet. And don't whine and say "could you just tryyyyyyy?" No. Why? Because I'll die. You'll die. We'll all die. And then you'll bitch at me, because I'm a sucky tank. What part of "I AM NOT A TANK" don't you people understand?
Yes, I know my gear sucks, thank you.
No, I don't have any other gear. Do you think I'd be walking around in sucky gear, if I had better gear to wear?
No, I really don't have any other gear. Yes, I'm aware that it's mostly tank gear, and I'm a DPS, but I just very recently learned that I was totally fucked up in regards to my spec/gear/rotation. Okay? I know you don't know that until I tell you that, but dayum, lay off me, okay? I've got the right spec now, and I've got a pretty good rotation, and now I'm working on getting the right gear, but that shit takes time and gold. So unless you personally want to run me through the necessary instances and/or give me gold, then kindly STFU after I've explained this to you, okay?
Also, don't insist that I join your group when I tell you that I can't run this instance. It's because I don't have the right gear, and we'll all die. A lot. And that brings up a hefty gear repair bill. And then you'll bitch about that and how much I suck.
Okay, that's it. :D