In case anyone’s wondering about the #showtooltip that Dvorkin added – this doesn’t affect what the macro does, only what you see when you mouse over the macro on your toolbar.

Once I knew the answer, I was able to find the /startattack command in Cogwheel’s guide. As far as I know, this is the only (putatively) complete guide to writing macros. You can find it at http://forums.worldofwarcraft.com/thread.html?topicId=3881820910

#showtooltip
/target pettarget
/startattack
/cast hunter’s mark

I hate instances, and I only rarely group (mostly to help out someone who asks me nicely). My simple macro is intended to ensure that my hunters are attacking the same target as their pets. It also saves a lot of time when you can’t see exactly what’s going on, but you know that pet hasn’t returned after the mob has died. I simply hit G (which happens to be the key I map this macro to), and I can immediately see (because of /target pettarget) what my pet is focused on. Moreover, I automatically attack it, which is usually (though not always) the best thing to do.

I use a variation of Lovemypet’s macro, above [which I am very interested in and want to go home and play with now]. This one toggles the pet’s attack instead of the player’s:

/petfollow [target=pettarget,exists]
/stopmacro [target=pettarget,exists]
/cast Hunter’s Mark
/petattack

One push casts HM on your target and sends your pet to attack it; a second push calls your pet back. Great for those AAAAH NOT THE SHEEP moments (though I noticed a while ago that pets now automatically break off attack on all newly-CCed mobs, not just trapped ones. Still, I am always fond of panic buttons).

/target pettarget
/cast attack
/cast hunter’s mark

This makes your hunter attack whatever your pet is currently fighting. The hunter’s mark line is optional, and you may want to omit it and cast HM manually, since it triggers the global cooldown and prevents you from using any other shot for about a second.

Note also that “/cast attack” is a toggle. If you call this macro when you’re already attacking the target (easy to do, in some circumstances), you will stop attacking! In theory, you should be able to fix this by writing “/cast !attack”, but this doesn’t seem to work, so I just live with sometimes having to push the button twice. It’s still better than attacking the wrong mob when pet is tanking 2 or 3, since the one you shoot at will immediately aggro onto you.