I get a lot of rescues in with mucky ears, the bottom line is if the ears don't smell nice, clean the canals with an alchohol based ear cleaner that will treat and evaporate. I make my own, but there are several commercial brands to choose from.
Step one - if your dog has hair growing out of the ear canal - pluck it out, a few hairs at a time. Poodles and schnauzers and their mixes are particularly prone to this. If will grow back, pluck it again when it does. If you are checking the ears weekly, it won't be a chore. I also like to trim any long hair on the inside of the ear flap to improve air flow.
Step two - if the ears smells yeasty, tip or squirt a little ear cleaner into the canal (1/4 to 1/2 a teaspoon despending on the size of the head) and massage the ear. Your dog will want to shake, let him after you have massaged it for 10 or 15 seconds. Then clean the visible parts of the ear with a cotton pad (I use make up remover pads too!) that has been dampened with the ear cleaner. Don't push the pad or cloth futher into the ear than you can actually see. Repeat for the other ear. If it looks dirty but smells clean, don't flush the canal, just clean the visible parts. If the ear looks and smells clean, just wipe with a damp pad and do a pretend clean - really important while they are learning the routine.
Step three - this is the really important part - give your dog a really yummy treat and a big cuddle for being so good!