I did:

01-10 Quest
11-16 Deadmines
16-20 Stockades
20-45 Scarlet Monastery
45-55 Stratholme (Scholomance is good too)
55-60 Ramparts

During RAF I did my boosting with an Elemental Shaman, level 70 (this was pre WotLK).
An AoE tank, or at least AoE class is a better booster, but anything that can clear the instance will work.

In Deadmines, each mini boss you kill, creates a patrol which wanders from the entrance (or wherever they spawn) towards the docks and back.
Once you get your toons to the docks, you are safe.
Alternatively, wait at the mini bosses for a minute or two, and then take the patrol out.

When you're boosting, you'll want to pull a bunch of mobs, and AoE them down.
And then another pack.
You'll eventually need to move the lowbie up.
When they're very low, getting even close to the mobs will cause a train.
But if there's AoE from the booster, that can save them.

Then exit the instance, reset it, and do the same thing.
Ideally, you want 12 minute clears.
As, after the first hour, you get a maximum of five resets per hour.

When you are in the later SM stages.
Run Cathedral, then Armory, then reset.
Then run Armory, then Cathedral, then reset.
You can leave SM at 40, but you won't really level any faster elsewhere then staying here till 45.