There are many signs (or symptoms) you will be able to observe if you suspect your dog has an ear infection. The more common signs include an unusual odor or foul smell coming from the ear and a colored (yellow, brown, or bloody) discharge leaking from the ear.
You may also notice your dog titling or shaking his/her head more than usual or scratching or pawing at their ear or trying to rub their ears against the floor or furniture. If you notice any of these behaviors in your dog, it is probably a sure sign your dog has an ear infection and a trip to the vet is a very good idea.