Hive mind: What advice would you give to someone who has to give a presentation to a non-technical person, and it's important that the listener actually understand the details?

How do you go about it? Specific tips appreciated. Pretend it's for a friend you care about.

(This is for an article. Ideally we could refer to you by reference for context and credibility, eg "an IT security pro at a midwest insurance company" or "aerospace engineer" so please give some kind of identification to use).