loveliketheflowers: Can you dance? I hope so, because otherwise the rest will make no sense.
Dancing is about moving with the music, allowing your body to flow and being in the present. The secret to good conversation is to dance with it. Go with the flow, be present and move with the words. Don't think, don't work it out, don't figure it out. Listen, then listen, and then listen some more. Say what comes up without thinking about it. At first you may filter it with your foot(ie: foot in mouth syndrome), but you'll come to know what to say without thinking about it.
If you want to know how to fake it until you make it though, you just said it yourself. "Be approachable." That's it. If you are in any situation, just be approachable. Be engaging, be inspiring, be open. Imagine being a particular way that you want to be, then go with the flow and let that into the conversation with you. Let how you *
really* want to *
be* become the music for your interactions.
And of course: Have fun.