Well, it looks like I'm going to write about tanking before healing. I hit 30 on the monk and picked up dual specialization; however, I didn't want to take the healing spec while levelling, since it has a different primary stat than the DPS spec.
On the other hand, the tanking spec has agility as its primary stat, and monks don't use special gear like shields. So it was very simple to spec Brewmaster and jump into a few instances.
I had tanked an instance a couple of times before, but it had been a while (I don't believe I've ever played DPS in an instance, incidentally). Fortunately normal dungeons are a complete faceroll now. The most difficult part was just keeping track of where all the mobs were. Although I did feel a little squishy when I pulled a tough group and Guard was on cooldown.
As an aside, Guard seems like a pretty poor name for a monk ability. It would be much better suited for a warrior or paladin. Unfortunately the names of monk skills generally feel a little phoned in; the Mistweaver tree is particularly poor for this, as it feels like half the abilities are just some variation on *blank* Mists.
When I play a healer, I am annoyed above all else by tanks who pull before I'm ready. In particular, I'm often in a DPS spec when soloing, so I have to change specs and then drink at the start of the instance. So I decided in advance that I would play carefully, watch the healer's mana, and ready check before the first pull.
Of course, this just meant that the DPS ran in and pulled instead. Oh well.