/cast [modifier:alt] Battle Shout; Heroic Strike
So let's break this down.
This simply displays the tooltip of either ability you specify.
/cast [modifier:alt] Battle Shout; Heroic Stike
Here we are specifying that you want to cast Heroic Strike, or Battle shout if holding the alt key. The same result can be accomplished using key bindings and additional action bars, but this way it takes up less real-estate on your screen.
This is easy enough to understand...
I've added this at the bottom of every one of my macros so I don't see the error crap flashing across my screen. It's nice because I tend to mash buttons rapidly.
So there you have it. One simple macro that if altered slightly I'm sure will suit your play style. Just change what abilities you wish to cast and you can cut your action bars in half.