Don't be scared. Just macro "New tank, please be patient." Pop the macro when everyone has zoned in, and proceed at YOUR pace. If the dps is antsy, that's their issue. Just remember that once the dungeon is done, you get a relatively instant queue and they have a wait. If you get a good group, keep running together. (Example: I'm a piss poor healer. Well, I was. Now, I'm pretty good at it, (on my druid, who I leveled basically resto in LFG), and unless tanks are being dumb (an increasing number, now that I'm in Northrend and level 77), we make it thru. If something happens, I remind the tank that I'm not a 6k geared druid, and I don't play one on TV. I remember a DK tank pulling the entire front room in UK, taking twice his health in damage in 2 seconds and then blaming me. The rest of the group was pretty quick to call him an ass.
To work on threat generation, I tend to grab my hubby and my kid and wander into the wilds and tell them to go ***** to the wall, while I taunt back, and try to maintain threat.
Any thing w/ a mana bar or that casts fear should be killed first. After that (there's an after?) most stuff is already dead.

