When I join a community I look for what they are talking about. I just started my blog two months ago and I want to know more tips on how to make my blog better as well as how to become a better marketer. There are many people here who have done just that and I want to learn more. I would say I look for information.
I also try to find out how many people are contributing to the community and have also joined.
Because I don't know too many people in my circle of friends who want to do what I do, I want to find people that share the same interest and drive to blog and make money online.