When I feel close to them and when there's a girl that interests me. I try hard to explain it simply from the scientific aspect and answer any questions. I found that using some scientific terms such as mood stabilizers, hypomania etc that most people don't know adds points to my explanation. "Oh you've searched it a lot!" I may seem a little wiser than I am but I don't want to do it on purpose!
In any case I believe it helps a lot to clear things up and decide who are the people that worth being around you.