Do you ever notice on new brake pads how they have the leading edge that is angled down. That leading edge is called a chamfer, and that allows the pad to reduce grabbing and squeeking. So basically you can use sand paper to make the leading edge chamfered again. If you google how to chamfer brake pads im sure you will find a tutorial somewhere about it. It is very easy.
Also why you are at it, you can remove the backing plates on the brake pads and apply some brake quiet lube and put the plates back on. When chamfering the pads you can also use a flat surface to sand the face of the pads to to remove any glazing or uneven brake wear to get a solid flat pad against the rotor surface.