A few tips on lower-level tanking:

-What folks said about using flash is absolutely true. Flash is your friend.

-Marking an attack order is also very helpful because it tells your dps where you are going to focus your hate generation. (If they go off your marks, sucks to be them, let them deal. If they spank it, they tank it.)

-Something that some folks may not know when new is that flash will generate hate while mobs are asleep and will not wake them. So if you have a thm/cnj sleeping things to help with hate management, don't go smacking it for hate build, but absolutely flash a couple more times.

-If mobs aren't asleep, tab onto them and smack them around a bit with some of your hate building combo. Rage of Halone once you have it. Tab thru the set, follow with a flash and you should be good.

-Do not use Provoke to establish initial hate. Shield lob for distance pulls; it generates more hate. All Provoke will do is put you at the top of the hate list +1. Good for taking hate off someone who stole it, as long as you hustle and follow it with more hate generation moves, but not so much for an initial build. It can be used as a very far distance pull, but don't depend on it as a hate generator. It is an emergency measure.

Low-level tanking can be hard because you don't have the full arsenal of hate management tools, but it's not impossible as long as your dps aren't straying off your marks and your healers aren't having to patch up too many people. Part of that is on you. Try to step out of any avoidable damage. The rest of that is on your dps not to be ouched. If everyone's working in concert, it should go smoothly.