Whats a tank?

[Eye_Gore]

First and foremost always have the d-bag blinders on.
Talk to the group upon starting the instance especially dungeons, communication is key for a smooth run.
Start with a Shield lob (if available).Once you get a mob gathered always Flash 2-3 maybe even 4 times to get the aggro up on you. 3 is usually the norm.
Rotating through the mob will surely help in maintaining aggro, especially if AOE's are going off.
Keep an eye on those aggro meters and the monster HP bars will give you an idea of who is attacking what.
If you see a monsters HP going down quickly and its not the one you are attacking, switch to that one.
Provoke those that you lose aggro on and is beating down someone, may need to have your attack rotation pre-charged for maximum aggro generation depending on your level
Marking targets, seems optional, most people will watch what you hit first and go after that.
The dungeon and your group ilvl will depend heavily on how hard you need to work to maintain aggro.
DPS can handle the hits if they are high ilvl in low level dungeons
Don't be afraid to ask your group for help, most people will help. I have learned the most from the people in my group, when asked. Of course you will run into that other person.
Good luck.