Defamation is defined as the speaking and publishing of false, distorted and misleading information about another, in a way that harms that person's reputation.
Libel is written or published information.
Slander is oral or verbal defamation.
It is advisable not to use the background stories or experiences of others in illustrations, without obtaining the consent of the person involved.
Be careful not to violate confidences shared in a ministerial setting, especially a counseling setting.
Always verify and double-check information to insure that it is true and factual. Even then, don't say or publish anything that would harm another person's reputation. Legal judgements regarding defamation can be significant.