Speaking from my own experiences of setting up a community garden in a public park in South London…….I heard about what was going on from posters around the park – there was already interest in setting up a community garden, and there was a call for a steering group to be set up to get things going. After we had formed a group, a representative from the local council came along to one of our first meetings to give us some ideas about how to go about things, and to suggest other groups/people that we might want to get in touch with. And it just snowballed from there really. In my opinion, its always best to meet people in person whenever possible. Maybe have a regular public meeting so people know where to find you.