Pop off the cap on the top of the faucet knob with a flat-blade screwdriver to locate the retainer screw underneath. On some faucets, a hollow set screw may be in the side of the knob. This type of screw requires an Allen wrench to remove.
Extract the screw using either a screwdriver or Allen wrench, depending on your faucet style. Pull the knob or handle straight up to remove it from the faucet and expose the valve stem underneath.
Apply plumber's grease to the threads on the valve stem.
Slide the knob or handle onto the valve stem and secure with the screw.
Twist the knob or handle back and forth to work the grease into the threading, stopping the squeak.