Cleaning your dog's ears is easy to do with a cotton ball and a small amount of witch hazel or other ear cleaners. However, most healthy ears don't need to be cleaned - a little wax is normal and should be left alone. Over-cleaning can lead to irritation of the skin in the ear and even to inflammation.
If you've noticed your dog's ears smell bad, if he scratches or paws at his ears, shakes his head, red and irritated, or they're hot with a waxy discharge, it could be signs of an ear infection. If left unattended, an ear infection could lead to hearing loss or a loss of balance. You should consult with your vet if you see any indication of an ear infection. They'll help identify the source of the problem and get you on track to get it cleared up, as well as to assess any other health concerns that need to be addressed.