Originally Posted by jhaber

As I understand this modern road brake pads should toe themselves in properly. For mountain bike pads I like to take a zip tie and pull the end throw the catch of the tie to leave a small circle a bit bigger than the pad. Then place the circle over the back of the pad (the end facing the back of the bike). Then squeeze the brakes to the rim with the zip tie still on the back of pad (the front of the pad should be touching the rim and the zip tie should be touching the rim in the back), adjust the pad to follow the curve of the braking surface, adjust the height of the pad, adjust both brake pads till they are similarly aligned on both sides of the wheel and they should be aligned and toed in perfectly.

I also find it helpful to adjust the bolt holding the pad to working tension and then recheck that everything is correct then tighten down to the proper tension. If the pad moves when tightening it down it probably means the bolt (for v brakes) holding the brake wasn't cleaned and greased properly before installing the caliper.