Q&A

 Master

I like to remove the caliper, and using a C-clamp and one of the old pads, press the piston back into the bore with the bleeder open to allow the nasty fluid in the caliper to drain onto a container. Then close the valve with the C=clamp in place so no air gets in, and proceed with pad replacement. Extract the old fluid out of the reservoir and refill with new fluid before pumping the brakes up.
NEVER, EVER, retract the caliper piston without the bleeder open because you will force contaminated fluid from the caliper back up through the brake system, through the ABS unit, if so equipped, and into the master cylinder contaminating sensitive parts causing big trouble for you.