In truth, proper care for your laptop bags depends greatly on the material that comprises it. If it is primarily leather, then you would condition it on a regular basis, just like you would do with any leather item. If the computer bag is nylon or another synthetic material, wiping up spills and trying to keep it away from excessive moisture would probably be a good idea. The manufacturer of the bag will also often have cleaning tips as well.
Generally speaking, though, it’s a good idea to clean up any spills and stains quickly, to use a mild soap and water, and to allow the laptop bag to air dry completely before using it again.