Without knowing exactly what you have or what shape it is in I can only give you these tips.If yours is like mine, I have a tube type consolette, you need to first remove the clip at the base of the spindle and pull off the platter. There you will see a small rubber wheel. If the rubber is brittle and cracked it will need to be rebuilt.
http://www.west-techservices.com/These folks can help you. If the idler is just glazed you can try cleaning it with isopropyl alcohol or a product called "Re-Grip, or Rubber Restore" which is made to remove the glaze and give it grip. This stuff can be had at a local electronics parts dealer. (Note: I doubt your local Radio-Shack would have it.) If the idler has a flat spot it must be rebuilt or replaced. The motor may need to be lubed. A good grade sewing machine oil will work but apply only a drop per bearing. If you are not mechanically inclined I would suggest you take it to a repair shop if you can find one. Chances are the entire mechanism will need to be cleaned and lubed in order for it to function properly. Regards.