I usually don't pay attention to what other people are saying on the plane, whether to each other or the FAs. Personally, I always try to smile and be polite. (Yes, I still try to smile even after losing a sale and 14 hours of flight time...

As for starting conversations... I used to try to start conversations with almost everyone I sat next to... that was just my personality. Now, though, I usually just say, "hi, how ya doin'" when they sit down and if they choose to take that as a conversation starter, fine, I'll chat. I've had some good conversations, and even met some people that I still keep in touch with. But I'd say the average is 2 people a year in that category (i.e. 1 person per 50 flights or so). I do enjoy a good conversation, and I love meeting new people... it's a major reason why I'm in the line of work I'm in and why I enjoy travel so much.