Code
#showtooltip
/cast [target=focus, help] Misdirection; [target=pet, exists] Misdirection; Misdirection
Quote
This will misdirect to your focus target, if that is friendly. Secondly, it will misdirect on your pet.
Alternatively, you can create a macro designed to cast Misdirection on a friendly player by name. Simply replace "Tank" with the name of the player you'd like to misdirect.
Code
#showtooltip
/cast [@"Tank"] Misdirection
I found these macro's here.