Generally, an infection is caused by moisture inside of the ears. Since Golden Retriever's have long ears, air does not circulate well.
Many people mistake the beginning signs of an infection for mites, as a few of the symptoms can mimic each other.
However, contrary to popular belief, dog ear mites are not all that common.
Cats are much more prone to mites than a dog is.
If your Golden Retriever is shaking her head, scratching her ears, or you can see an excessive amount of dark, brownish-black ear wax build up inside her ears, this can be the beginning symptoms of a dog ear infection.
As the infection continues to progress, the inside of her ear will turn a bright red, and you can actually feel the heat coming off of it. There may also be small blisters inside.
She may get a yellowish-white, pus discharge.
As this drains from her ear, her face will also become infected.
You may be thinking that it takes awhile for the symptoms to reach this stage, but an infection can happen incredibly fast, and can go from not realizing she has one, to being extremely severe, within a day or two.