Although people don't always think of washing and wood in the same thought a simple wipe down using warm, soapy water in a damp (not wet) sponge can do wonders!
I would advise not sanding unless you know what it'll do. Sanding will remove material from the high spots and won't touch recesses, dents etc. and will tend to reveal much lighter bare wood where it abrades, which gives a very characteristic (and not particularly attractive) look in many cases.
Do bear in mind that if you expect it to withstand spills (even plain water), hot plates and other normal food-related wear and tear that you really do need to give the surface a proper finish, just as you'd expect to have on a commercial kitchen table. Just wax is generally not sufficient protection for a working table unless you don't mind that it gets stained, and if you wax first you'll have a devil of a time using anything else afterwards.
