I use these couple of macros for tanking and they're a wonder.
To make new macros press ESC -> Macros -> choose Character Specific Macros -> New -> choose a name and an icon -> enter the macro commands -> grap it and put it anywhere in your action bar ( some macros need a key binding for it)

This one is for starting a boss ( certain bosses can't/shouldn't be charged with this macro):

/script CancelPlayerBuff("Blessing of Salvation")
/cast charge
/stopcasting
/cast defensive stance
/stopcasting
/cast bloodrage

Just go to Battle Stance and press the macro and you got yourself alot of rage at the start of a boss fight

This is one of the best macros ever ! (you need to bind a key for this macro)

/cast [target=mouseover, exists, harm] Sunder Armor; Sunder Armor

This macro is very great for tanking multiple targets without changing your MT target,just mouse over the mobs or thier health bars and click the binded key for it and you've got a sunder on that mob !