1) Ignore everyone else in the group: I don't mean don't talk to them, I mean pretend that they only exist to carry you through the instance. Do what you feel your role is (tank, dps, heals) with total disregard for the fact that there are 4 other people there. If you're a tank, pull way too many mobs. If you're dps, attack any mob you feel like. If you healer, feel free to not pay too much attention.
2) Blame everyone else: If you're the tank and you pull too many mobs, it's the dps' fault if they pull aggro off you. If the healer can't keep up, they must suck. If you're dps and pull aggro, the tank sucks for not holding aggro on the mob you're attacking. If you're the healer, it's everyone else's fault if you run out of mana even though you never thought to mention that you're low.
3) Make sure everyone else knows how much they suck: What good is blaming someone else for a fail group if you can't tell them? Make sure you use words like "noob" "fail tank" "fail heals" "lame" "loozer" "asswipe" etc... make up words if you'd like. If they don't know what the word means, it's their fault for not being awesome.
4) Do everything you can to get other people to drop group: People are much more likely to drop group instead of kick you. This is your best weapon of douchebaggery. Never forget that people can't hear their own apathy over your awesome. Oh, and if you can get a healer or tank to drop group, then you have to wait a while for a new one. This is a big win because it hurts the rest of the group too.
5) Continue to call names: Why should you stop saying how much fail someone brought to the group just because they quit? Let everyone else know. This should make them work harder because they'll know if they don't step up the awesome, you'll make fun of them too.
6) NEED on items you couldn't possibly use: If all else fails, step up the douchebaggery. This step is really only recommended for expert d-bags. If you need on too many things, someone will vote to kick you. You have to need at just the right times. Pick a few green items early on. Most people won't say anything because "hey, it's just a green". Once again, apathy works to your advantage. By the time you ninja loot the epic off the last boss, it's too late. Make sure to say something to piss everyone off before you leave.
With cross-realm pugging, there are literally THOUSANDS of people out there for you to piss off.
*god i hate random pugs*