This article is from the Dog Supplies FAQ, by Cindy Tittle Moore with numerous contributions by others.
In general you want to get ceramic or metal food dishes. Plastic food
dishes acquire microscopic scratches in which bacteria flourishes. You
should wash the food dishes frequently, just as you do your own.
Always supply fresh water with each meal.
If your dog has long hound ears, you should get the cone-shaped high
dishes that help keep the ears out of the food and water. Otherwise,
any dish will do fine for your dog. There are lots of cute dog dishes
Some of the larger breeds should have their food dishes elevated to
reduce strain on the neck and back. Most mail-order companies carry
metal frames for dishes. You can also try wooden boxes. Another
possibility is to obtain traffic cones and cut the tips off -- food
dishes then fit snugly on top.