One thing to keep in mind is that Battle stance has a built in 20% threat reduction, so you want to stay in defensive stance as much as possible.
As someone said above, make sure you have 3 points into Tactical Mastery, and 2 points into Improved Charge.
Another thing to consider is Anger Management (which requires 5 points into Tactical Mastery). There is a hidden bonus to this talent which generates 1 rage every 3 seconds passively. This is a pretty big help.
For aggro the best thing I have found is to charge in, hit my Defensive Stance macro, which also casts Shield Block. This should almost instantly proc Revenge, which is more threat than Sunder Armor (confirmed). Keep spamming Shield Block, and using Sunder Armor between casts and using Revenge procs.
After getting Anger Management I found it best to go into the Protection tree and get 5/5 Shield Specialization, and Improved Bloodrage. The Shield Spec will actually end up giving you quite a bit of rage because of the 100% chance every time you block to take 1 point of rage. Imp Bloodrage also helps a ton when you need to toss out a couple extra Sunder Armors. Aim to keep Bloodrage on cooldown almost 100% of the time.
Demo Shout is almost pointless to cast for Threat. However it is a very decent AoE debuff and should be used when tanking multiple melee mobs, but never depend on it for aggro. I think rank 1 generates about 30 threat on each mob it hits.
Battle Shout rank 3 generates 17 threat to all mobs in the encounter PER PERSON IT BUFFS. Which is also why you see many veteran tanks taking the talent Booming Voice, so you can catch your ranged DPS and Healers with it. Max rank Battle Shout generates 70 threat per application. This is actually a decent way to gain AoE threat, but NEVER expect to hold threat on a mob with it if a DPS is going ham and you are not actively attacking it.
I think the biggest thing to keep in mind while tanking low level dungeons is to stay ahead of your group. Always make sure you are the first one in, and have a Shield Block and Revenge on the mob before anyone else gets there.
Another tip is to bind Skull Target to a hotkey. Use it on EVERY pull.