When I was a kid hanging out in a front-end alignment & brake business, I'd watch my father deal with squeek complaints as follows:
First, he'd make sure it wasn't the wear sensor rubbing on the rotors, indicating that it's time to replace the pads.
Then he'd use copious amounts of water to spray out considerable amounts of brake-pad dust from wheel assemblies. He'd test drive it with the customer to demonstrate the lack of squeek. He did this "for free."
Then he'd tell a customer to drive it for a few miles and if - after some braking activities - the squeek returned, the customer could check for dust.
If dust was found, the customer could then return and pay my father - through the customer's nose, if the customer was disagreeable - to remove the pads and coat the non-stopping surface of the pads with some goo that would exorcise the squeek demon.
Pretty girls never had to pay through the nose. I didn't understand that until much later in life, but I still believe in squeek demons.
-Jon