Pls check out http://www.clockies.com. Discover & share interesting future happenings with friends. It is really cool. It’s like a time machine when you have a lots of friends on it.
I promise we do it in whole new different way of sharing. YOu can follow TV Shows, NBA, Movies. and share the events that are the most interesting to your friends. So you will get recommendation of what to do from friends. Like for instance I got a recommendation that 2 1/2 are airing next week
Ok, just to be clear. It isn't me you need to tell but everyone. No one will sign up to something, no matter how good it is if they don't know anything about it. So my suggestion is to explain your service. This might be with text but you could also use videos or screenshots.
Also, discovering and sharing future happening with friends sounds like something that facebook already does well.