Very, very slowly for the same reason you don't squeeze the soap too hard. I was lucky in that my wife, who came from an extremely conservative background and was very interested in exploring life and different experiences. The conversation was fairly easy and we ended up at the old Marquee within a few months of having that conversation. You might already have some clues as to her acceptance of the conversation. If she is a firm believer in monogamy..... The answer to your question might exist in the strength and openness of your discussions in other areas of life. That is a reality. If it isn't strong and open, then swinging will cause you more pain than pleasure because you will have conflicting opinions about people and what is acceptable in your swinging experience. Choose a very soft intro to the conversation if you have that openness and trust. Timing? She must be very relaxed. Content? Ask her if she has ever fantasized about including other people in her sexual experiences. That sounds harsh, but a no is a no. Discomfort and doubts? Back to the relationship thing. Talk. Talk. Talk. This is certainly not the Holy Grail of Swinging, just my opinion. You know your lady better than anyone else, and that is key. I have given my opinion, hopely others will join the conversation.