2. Be Responsive
One of the worst things you can do when a conflict arises or someone has a complaint about your business, products, services, etc. is ignore it. In most cases, some kind of response should be issued immediately, even if it's just a brief statement that you'll look into the issue.
If you wait until you have all of the information necessary before reaching out to the unhappy party, they may end up not only unhappy, but now also angry. Keep the lines of communication open in all situations by being as responsive as possible and making sure the people reaching out to you feel like their issue is important to you.