The answer is rather simple: don't be an idiot. If you are even half paying attention and aren't a complete scrub, you'll probably get as far as you want to in WoW.
I'm going to do the Aged Grandfather thing and embarrass my guildies by telling stories about them now. The long and short of it is that they aren't scrubs, and don't know how good they really are.
Take Gorgor, our Hunter. He takes no end of flak for being a Hunter. Let's face it: everyone makes fun of Huntards. The class will be forever prejudiced against and stigmatized. But the thing is that Gorgor is actually the exception to the rule — he's a good Hunter.
I'm not going to say that his pet has never accidentally pulled aggro, or that he's never made any mistakes. Instead, his mistakes are so few and far between that you tend to forget that he's there.
Tanks and healers get to be superstars when they save the day, but how often do you think “dude, that Hunter just totally saved my butt!”. Not often. And yet, I can think of a number of times that Gorgor has been there for me, whether it be bandaging me while I DPS because the healer is focused on the MT, or laying down a Freeze Trap between my Mind Controlled mob and my body, or whatever.
Gorgor doesn't raid much — having little kids will do that to you. But after two weeks in Kara he'd picked up enough blues and purples that it looked like he was ready ...
Last night with us, Gorgor ran his very first Heroic.
The dungeon in question was Arcatraz — one of the hard-mode Heroics. Not only did he comport himself admirably, he managed to top the damage and DPS charts. Oh, and he died less often than everyone else. Not half bad, I think.
And sure, it irks me to no-end that this lowbie Kara-level Hunter can out-DPS me. I'm not bitter. Not at all.
But I digress.
Then there's Groosalugg, our Protection Warrior and MT. Groos pines for the days when he was specced Fury, and half-heartedly threatens once a week to respec back for good. He raids with roughly the same frequency as Gorgor, which is to say some Kara and maybe one other dungeon per week. I believe that Warcrafter ranks the two of them within a couple of gear points of each other.
And yet, for that infrequency and Kara-level gearing, Groos is an exceptional tank. He's exceptional to the point that I'll give him my highest praise: even with him in pre-Kara blues and greens and me in all purples at 1175 spell damage, I still had a hard time pulling aggro off of him. Even when I could, he'd almost always get it right back before I got squished.
On his first outing to Kara two weeks ago he was OT for most of it, switching to MT when it made more sense, and we one-shotted our way through almost the entire dungeon. On his first time ever seeing Maiden he was the MT and pulled off the kite-to-pop-the-healer maneuver flawlessly.
I'm lucky to run with such great people. We're calm on Vent. We handle wipes well. We take our time and think things through. PUGging is made all the more reprehensible because I know what it's like to be part of good group.