Summarize this article:

Daily cleanings of your dog's food or water dish are an important step in keeping your dog healthy. Depending on what you feed him, you may have to clean his food dish multiple times a day. For example, if you feed him wet food only, a combination of wet and dry food, or raw food, clean his food dish after each meal.  If you feed your dog only dry food, then cleaning the food dish once a day may be sufficient.  If you have outdoor dogs, or use one water dish for multiple dogs, clean that dish several times a day.  If your dog's food and water dishes feel particularly slimy, consider cleaning the food dish after each meal and the water dish twice daily.  Food and water dishes can also accumulate saliva, dust, and debris. In addition to possibly making your dog sick, he may not even want to eat or drink out of the dishes if they look too dirty. Not all food or water dishes can withstand frequent washing. Over time, less durable dishes can develop scratches in which bacteria could grow and make your dog sick. When you have cleaned the food or water dishes, look them over closely for scratches.  Replace any scratched dishes.  Stainless steel and porcelain dishes are very durable and can handle frequent cleaning.  Ceramic and plastic dishes are not good choices because they are very porous and can harbor bacteria. In addition, plastic dishes get scratches very easily. It is not enough to keep your dog's food and water dishes clean—the area  around  his eating area needs to be clean, too. To clean the floor in that area, mix together equal parts vinegar and water and mop the area every few days. Alternatively, you could place a rubber food mat under the dishes to collect excess food and water. Wipe down or hand wash the food mat each day to keep it clean and prevent bacterial growth.

Summary:
Clean your dog's food or water dish every day. Inspect the food or water dish for scratches. Clean the area around your dog's food and water dishes.