There's a stack of disciplines that comms people can learn from. Not least the art of online community building. It takes time. And effort. And simply building it doesn't mean they will come. But as the web increasingly becomes a channel for everything - not just comms - these are skills to look at.
1. You must have a community manager. You absolutely must have someone who wakes up worrying about your community every morning.
2. Your community must have a purpose. Your community must have a purpose that matters to the people you’re trying to reach. You shouldn’t be creating the purpose, you should find a purpose a lot of people care about and build a community around it.