How to align the PS bracket so the belt runs true

Finishing up my Slant-for-warmed-up-Slant swap...

The Power Steering pump bracket has too slots that allow the bracket to be adjusted.
I'm assuming this is to allow one to make sure the belt runs true - so, how do I set the alignment properly so I don't end up throwing belts, wearing out bearings, getting squeaks, etc.?

Do I just put a belt on and eyeball it? straight edge (if so, how/where)?

Thanks!

John