Vacuum the dashboard area of the car, just as you would the floorboards and mats. A shop vacuum is great for this, but a standard household vacuum will work just as well if you use a nozzle attachment to get back in the corners against the windshield.
Look carefully to see if the vacuum picked up all the visible dirt. If not, use a toothbrush, soft cloth or even a cotton swab to remove any stubborn dirt that needs a little extra nudge.
Wipe the dashboard down from one side to the other with a clean damp cotton cloth, micro-fiber cloth or any 100 percent cotton cloth designed for auto cleaning. Be sure that the cloth is only slightly damp and not soaking wet.
Use an auto interior cleanser for extra help with dashboards that may have something spilt on them. Follow the directions recommended on the auto interior cleansing product. Be sure that the cleanser is an auto interior cleanser and not a household cleanser.
Dry the dashboard off thoroughly with a clean dry lint free cloth.
Apply a protective coating on your dashboard if it's exposed to extreme sunlight or lots of dirt and dust regularly. Purchase your protective coating products at an auto supply company and follow the directions recommended for your type of dashboard materials.