All the replies so far have been great, I just want to mention that while you're running casual content/leveling dungeons and stuff you can "abuse" some situational abilities to make your life substantially easier.

Every tank has an invulnerability CD you will almost never use unless you're raiding or doing ex trials, they give you 8-10 seconds of invulnerability you can use for bigger pulls without putting too much stress on your healer.

Arm's Length is also nice for trash pulls, again you won't need it unless you're doing raid or trials, and it's really nice for bigger pulls because it gives a slow debuff to all enemies that attack you.

Also, you won't know it the first time you go in a dungeon, but if you pay attention to what surrounds you, you'll start noticing some dungeons have little details that help you manage packs, like environmental damage that would damage you also putting debuffs on mobs and such.

Good luck and happy tanking :3