In 2009, a strange Facebook account appeared out of nowhere and friended people en-masse. The name on the account was Junko Junsui, and she had a message for anyone willing to listen.
I'm no lawyer, but I've watched enough TV to think I know how to coach a witness. Mostly, shut up. Answer the question and don't say any more than you have to. Don't volunteer anything. It'll only make things harder for you later.