We recommend rubbing alcohol.  It eliminates moisture that may get trapped from swimming or bathing.  Excess moisture is the most common cause of ear infections.  You must be sure that there is no irritation in the ears prior to using alcohol.  If there is pre-existing irritation or breaks in the skin within the ear the alcohol can be quite uncomfortable.  If you aren't sure if irritation is present or if an odor is present, you should visit your veterinarian prior to attempting to cleaning your pet's ears.