Record washing machines are expensive (my VPI sells for about $500), but if you have a large collection of old records, it's worth the investment. The improvement in sound quality is tremendous.

The mmachines all work in a similar manner. Brush on the cleaning fluid, and then let the machine vacuum the crud out of the grooves.

If you can't afford a michine, use cleaning fluid (Disc Doctor and Record Research are two good brands) and wipe the disc with a lint-free towel. Or rig up a shop-vac to suck the fluid out of the grooves.

If you want to make your own fluid, the Library of Congress has a recipe that is essentially three parts distilled water, one part lab-grade isopropyl alcohol (not drugstore stuff, 95%+), with a couple of drops of tergitol or some other surfactant.