I always align calipers by eyesight. I just get behind the caliper and look at the space between the pads and disc and, with the bolts lightly tightened, center the caliper with my hands. When it's in position I tighten the bolts slowly alternating from one to the other.

If I see I can't correct the problem because the rotor is misaligned, I watch closely to find which part rubs and bend it back with an adjustable spanner.