It's funny. I usually don't make it common to tell on a first date, since in my opinion that is heavy first date material. The last first date I went on (who turned out to be my current boyfriend) asked me what the green bracelet on my wrist was about (it says Life. Pass it On. and is for organ donation). I had to make a split second decision and decided to spill. I kept it light, the basics, I have CF, and I got a transplant. And that was it! Clearly if it's meant to be it won't bother the other person or even cross their mind twice. It worked out for me!