Some OCers make little "business cards" that state some "fun facts" (!) about OCing and why people do so. Once in a while you will find that topic (about some sort of hand-out) coming up in the forum.
So besides having a conversation with someone who questions an OCer about his/her carrying, the OCer also gives the person a card.
BTW (and sadly), it's been in the 70s here daily, but Merry Christmas to you all in cold Colorado anyway!