I pretty much parrot everything here.

Unfortunately, GLD at Lvl 20 is rough for tanking IMO. My secret was to mark mobs when I started a pull. If the DPS can't kill by numbers, I let them tank it. Otherwise, Shield Lob is good when you need to stun an ability (Spoiler: The handmaidens in Haukke Manor when they use the "Dark Mist" ability). Either way, like others have said, PROTECT YOUR HEALER. (especially if they know you IRL). I run with someone who heals as I tank, so we have an "understanding" (never let them die).

It gets easier when you pick up Rage of Halone (level 30), where you're just going to combo 1 mob, then the next, then the next, flashing inbetween, n repeat.

IF you're starting tanking, try out MAR. I'd never tanked before, and I find it's easier to get/hold aggro. Buuuut, you lose out on survivability later on (yes, I know the thread, but different strokes n all).