ok squeeky brakes 101, number one cause is the pads are low and the wear indicator is scraping the rotor, next common cause is moisture corroded the brakes (think rust after storms) and you're hearing that break loose, third common is the caliper slide pins and/or the caliper piston are binding up causing the pads to not fully release the rotor
now those are the common "squeeky" items and causes. to diagnose with out completely removing the brakes you can look for imperfection in the rotor face (grooves, gouges, pits, corrosion, etc.) if those pass then look through the top of the caliper at the pads if one pad is significantly worn but the other is new looking i would suspect slide pins and/or the caliper piston assembly. if those all pass then it could be inferior quality steel and pads. for brakes raybestos is good quality and priced nicely.
