The best way to prepare for challenges at your library is to have policies and procedures regarding collections, programs, meeting rooms, etc. that are regularly reviewed, updated, and approved by your governing body. Policies should be available on your library's website so patrons can learn about your policies regarding their intellectual freedom.
In addition, all library staff should read the policies and be trained on the procedures. The policies, procedures, and any accompanying documents should be kept in a place that is easy for all staff to remember and access when they are helping a patron who has a concern about intellectual freedom issues.