I went from playing a rogue to leveling up a prot paladin.
She's only level 61 now and soloed almost the ENTIRE time.
A few times, I had a guildie friend run around questing with me on his rogue and I have to say, it is NOT good practice for instance tanking. You simply cannot build up a rhythm on a mob that the rogue can down with you in 2 hits. The only exception, I'd say, would be on perhaps those elite quest mobs that take 2+ players. I got a nice chance to practice "real tanking" on a level 63 elite with a warrior friend when we were both level 60. That was a real eye-opener.
After that, I dove right into Hellfire Ramparts and then Slave Pens. It's good fun.
I guess the best advice, apart from reading the maintankadin site (I still need to do that - it was recommended by a former guildie tankadin), is to get a good group together and just DO it. I was so scared I was going to blow it when I went into Ramparts the first time. It was a real confidence booster to go in with a resto shammie friend and take out the first few pulls with just the two of us. It was an even bigger confidence booster when we got 3 level 70 friends in and cleared the instance and I was able to hold aggro against a 70 prot warrior and 70 warlock!
Oh, and macro the target of target taunt.
*nod*
That was awesomely amazing in Slave Pens last night.
And I don't usually use macros.
-T.