Sixth, nothing will make you a better tank than just learning the content and practicing. You can learn it as a dps, you can learn it in solo duties with the trust npcs, you can even learn as the off tank, but once you really understand the fights, they become so much easier to manage.

Seventh, if you are new to tanking anything and there's more than one tank, let someone else tank it while you learn. Just make sure you have more aggro than everyone else except that tank, and you'll do fine even if they mess up. You definitely want to be ready to step in if they die, though. Provoke is your best friend in raids.

Finally, deaths happen, wipes happen. Try to make sure you're not the one causing them, but otherwise just pick yourself back up and get back to killing. Complaining doesn't kill things faster. Unless someone is really making the content difficult to get through, it's probably just gonna be an argument you don't want to have o.o;

That's my advice, anyway. I just do not have the time to type it out in dungeons while people are trying to kill everything.