You will need clippers small enough to enter your dog's ear. Consider also having a soft damp cloth for cleaning and some treats on hand.
You will need to secure your dog's head so he does not jerk it, causing injury, or try to run away. You can use a partner to hold his head or consider attaching him with a leash and harness to a secure surface.
Start with a treat. This sets this awkward grooming tasks off on a positive note.
If your dog is nervous, scared, or anxious about clippers, turn them on, let him hear the sound, and hold them up against his neck so he can feel the vibration and hear the noise close to his ears. Feel free to give him a treat during this task so he is associates a delicious treat with the sound of the clippers.
Hold the clippers inside one ear while pulling the outer ear away from your dog's body with your other hand. Try to clip as much fur as you can from inside the ear. Be cautious of any folds and wrinkles hidden inside that ear. Your goal is not to shave it but to just shorten the fur inside the ear.
Repeat the above step for the second ear. Be cautious of any folds or wrinkles hidden inside the ear underneath this ear hair.
Check both ears for any additional areas that require trimming or clipping. If you feel scissors or hemostat would be better to trim these areas that are left over after clipping feel free to use scissors to clip extra fur. You can also use your fingers or hemostat to pluck any fur leftover.
Dampen a soft cloth and use it to wipe out to the interior of your dog's ear. This should remove any excess fur left inside the ear. Try to get out as much fur as you possibly can to avoid any debris inside the ear canal which could potentially cause pain or infection.
End your ear grooming session with a reward for your pup. Save some high-value treats for the end of the session to ease any pain and help your dog get over any anxiety caused by trimming the fur in his ears.