When soiled, machine or hand wash in warm water with mild detergent.  I get the best results by wetting suede and using a bit of dish detergent.  I scrape off any bits of food and scrub gently with a dishcloth or whatever you have.  Rinse, reshape, and lay flat to dry.  I've been guilty of using them wet too - it's okay - they're really durable and they don't create steam.