...hence the adjustment is a bit of a black art, compared to hydraulics (where both pads move). You get two stages of braking: firstly as the moving pad presses against and deforms the rotor, then as the rotor contacts the stationary pad and is gripped between them. Fiddling around with how much space there is between the rotor and the two pads changes how quickly the latter happens. Make it happen sooner and you get strong, possibly 'grabby' brakes. Make it happen late and you get nice smooth modulation, but possibly reduced braking force.
The real art is getting really strong braking without excessive rubbing from the stationary pad - if the rotor's out of true, this becomes really difficult.
I've recently upgraded to BB7s from some older Tektros, and found that following the BB7 fitting instructions to the letter gave pretty good results. They're also much easier to adjust.
My main advice would be not to get too hung up about slight rubbing when you first fit them. If they're just making noise, but the wheel is spinning freely, and the brakes appear to be working well, don't get hung up by trying to adjust things to eliminate the noise - go for a ride first, preferably incorporating some nice hard braking, and see what happens. I found that the rubbing noises stopped (and the braking performance improved) once the pads had bedded in a bit.