Death Knight Heal Pet Macro

Try:
/cast [target=pet] Death Coil

You might have to put your pets specific name however, i.e Åvatar's Minion or w/e its called.

P.S. If you can get your pets name to work, you don't have to actualy change your target from w/e your attacking, it will just cast directly on your pet.

"Attack" Pet Macro (Shift+Forward-Mousewheel)
#showtooltip Gnaw
/cast [target=focus,exists,harm,nodead] Gnaw; Gnaw

"Retreat" Pet Macro (Shift + Backward-Mousewheel)
#showtooltip Leap
/target YOUR_DKs_NAME_HERE
/cast Leap
/petpassive
/petdefensive
/targetlasttarget

I like using the "Retreat" macro when AoE grinding quest mobs... send the pet towards the farthest mob, then use the macro to get him back next to me and drawing in a couple mobs into my AoE kill zone. And both have their obvious PVP uses.