This being my first MMO altogether, I wasn't at all used to the tanking mindset, even if I knew the base concept of tank-healer-damager-(support). Plus I did a bit of forum reading once I realized my class was a tank :p So I knew what my purpose in the group was. But the first dungeons I did, as well as when doing any dungeon the first time, I didn't mind saying it was my first time there, and if any of the more experienced players could help out it'd be awesome. I think first Sastasha run I did together with my flatmate, the other DPS took the lead and 'pointed the way' where I should go, plus marked important enemies.

A bit later on, when I was comfortable enough even my first time in a place to run ahead, I'd still ask (if I saw level-synched people or just generally people who appeared to know the dungeon) if there were any enemies that should be killed first and if so which ones and/or 'could you mark them for me? =D'

Nowadays, I only mark targets if I have newcomers or if there are enemies that should be killed first that I know people tend to ignore. Otherwise, I do my AoE aggro things, and then hit on the mob that takes the most damage :p Or tab between them or continue AoE aggro if I have AoE-happy DPS. It's usually easier for me to switch to the mob the dps are focused on than to stick to my mob and then rant at dps for not switching target ^^; (But then again, I have more the mindset that I'm there to support the group by protecting them, not to lead them and force them to play My Way. I'm also usually one of the first to volunteer for OT duties in 8-24-ppl stuff, and actually grab adds instead of poking the boss in the side :p Gotta protect the squishies, no?)