Alot could depend on what your enclosure is made of. If it is a non-porous surface, most people use a 2% bleach solution. You have to rinse it THOROUGHLY, and preferably let it air dry 24 hours before putting your snake back in. Frequency depends on how messy your snake is (poops in water dish or all over the enclosure, for example) and what your substrate is. Weekly to every 2-3 weeks is probably about average, for a thorough cleaning. Spot cleaning is as needed.