I don't turn the rotors when replacing the pads. I will sand the faces of the rotors with 80 grit to give them some bite to wear into the pads. The swept area of the rotor is pretty constant. The issue is getting the pads to conform to the old rotor.

I think the most important thing when replacing pads is to break them in gently. If you get them too hot right away the glue boils to the surface and glazes the pads. Use them as required when you need to, but if you can take it easy for a day or so they will give a better feel. If they get glazed, they have to be removed and sanded.

You can keep the brakes from squealing by putting a thin smear of RTV on the back of the pad. It damps the vibration.

Greg