Here are two vet approved methods (at least they are approved by two of the vets I talked to):
Method One: Moisten a cotton bud with a little mineral oil and gently swab the parts of the ear that you can see (don't go any deeper).
The mineral oil lubricates the ear skin and also has the side benefit of suffocating any ear mites if there are any in there. Don't use too much oil otherwise it will make the fur around the ear greasy looking for a few days. I like to first use a cotton bud with a mineral oil, then follow with a dry cotton bud.
It's only necessary if there is brownish gunk visible. If she has nothing in her ear, not necessary to do anything.
Method Two: Moisten a cotton ball with a little warm water. Wipe gently in a swirling motion.
My Russian Blue says she likes the first method the best.