We just tried Mr. Clean's Magic Eraser on our turntable needles and the improvement in sound is significant...less veiled, more dynamic, better fidelity. IMO, everyone who owns a turntable should pick up a package of Magic Erasers, especially if you don't have a method of keeping your records clean. These eraser pads are about $5 from anywhere. Gently push the magic eraser into the cartridge needle so the needle slides in and out of the eraser pad three or four times. A case could be made for doing this after every side to maintain maximum performance.
Dirty needles are bad, mmm-kay.
Have a great weekend,
Chris