What's a good way to address an improperly placed dental crown?

Consult your dentist. There is a warranty with every crown by doctor and lab. However the warranty only covers a crown if patient is compliant with hygiene and preventive care.
Ask your dentist. Ask your dentist if you can have it remade under warranty. How old is the crown? Who told you it was problematic? More details needed....
Go back. Go back to your dentist and demand the quality work. And after that go to another dentist to check their work.
Improperly placed? First off, how do you know it was 'improperly placed'? Are you having symptoms? Pain? Swelling? Etc? If so, you need to see your dentist asap. It may be that the crown 'bite' simply needs adjusted. If the problem is more serious than this, perhaps the crown will need to be adjusted further, or remade if you're having tooth problems. If you only don't like the look of the crown, see your dentist.