Here's what I do, might not be text book but it works for me. Attach the pads but don't tighten them up, pull the brake on really hard (if you're doing the rear, pull the cable near the tob tube instead as it's a bit of a stretch - same effect) and allow the pads to find their flat-to-flat mating position against the rim. At the same time, tighten up the allen bolt again, once they're almost tightened up, loosen the brake and hold the pad with your hand to stop it spinning (doesn't always happen) while you tighten the allen bolt that last little bit.
I never get pad squeal this way and get excellent modulation. I used to use a toe-in tool (AKA piece of cardboard or plastic) to get a degree of toe-in, but I've never seen the benefit on a road bike).
Dave.