Use a pet shampoo. Pet shampoos are pH balanced to be gentle on a dog's skin. Using a human shampoo can cause your pet's skin to become dry, itchy or flaky.
Bathe the dog infrequently. Dogs don't need a bath very often; once a month is plenty. A veterinarian or groomer can advise you on how often your particular breed of dog should have a bath. Some dogs shouldn't be bathed more than two or three times per year.
Keep water away from eyes and ears. A dog's eyes and ears can be very sensitive to water and shampoo. Cotton balls can be placed loosely in a dog's ears prior to bathing them to keep water out of their eardrums. Remove the cotton balls when the bath is done. Shampoo in a dog's eyes can be very irritating; use a product like paralube to keep the water away.
Rinse thoroughly. Thoroughly rinsing your dog is very important, especially if they have a long or thick coat. Residual shampoo can irritate the skin causing the dog to itch. Soapy water left between their toes can also be irritating, causing them to lick or nibble at this tender skin.
Dry the dog thoroughly. Clean, dry towels are the best way to dry your dog after their bath. If you let them outside before they're dry, you might find that they find a dirty patch of ground in which to roll, causing them to get dirty again.
Giving your dog a bath can be a fun time for both of you. Just remember to keep the water warm, not hot or cold, and be as quick and thorough as possible.