Here are some tips:

-Be friendly with the healer(s). In most cases, they will back you up in any group drama (sorta a golden rule).
-If a DPS runs ahead (or that rare healer) and aggros things complaining you're pulling to soon, let them die. Most healers recognize this crap behavior from DPS and won't heal their stupid selves and will back you up in case of drama (Golden rule).
-You set the pace. If everyone wants to speed run and you aren't comfortable with it, screw 'em. Again, be friends with healers. If you feel good about speedrunning but the healer has reservations, err on the side of caution and take it slow. You won't run out of time, dungeon timers are very generous.
-Stand up for yourself. Lots of DPS and those rare healers will give you crap over the smallest things. Don't take that crap. Stand up for yourself. If all else fails, leave. The stress of dealing with that crap on top of tanking just isn't worth it.
- DPS are expendable. If someone is giving you grief, vote kick. If it's a DPS, you'll get a rep in seconds. Healers may take a minute or to. Tanks are super rare. If the tank leaves, generally the party's over.
- Grow a thick skin. Tanks get blamed for everything under the sun.

Overall, tanks have incredible power, just don't let it go to your head. If a group is pissing you off, leave. Don't hold them hostage going "neener neener". It's ok to be a nice tank, but just remember, people WILL take advantage of you and push you around if you're too nice. If all else fails, get a buncha friends to do the dungeons with. Going into the DF solo is scary.