Paragraph III of ALA's Code of Ethics says:
We protect each library user's right to privacy and confidentiality with respect to information sought or received and resources consulted, borrowed, acquired or transmitted.
This means that you should not talk about patron's requests outside of the library environment. You can't, for example, tell your spouse about who dropped into the library to ask how to file his own divorce. You should not discuss any questions (with anyone!) that would violate a patron's privacy.
In discussing questions with your fellow employees, make sure that other patrons can't overhear, and that you are doing so for professional and not personal reasons.
You must not give out information on what books a patron has checked out without a court order. (Minnesota law protects this right to privacy. See the Minnesota Law on Confidentiality of Library Records.) If you have such a request from a law enforcement agency, refer it to your supervisor.