We have been building social / real estate / product / sports / religion and all kind of communities for our customers. We see some very successful one and a few that do not make all the way through. It's time we share of the ideas with you that helped the successful.
Great ideas are just ideas without you make them work. When you have your community strategy make sure you convince everyone else in the team as well.
Create a strategy before you start calling vendors to build the community or find a vendor who can help you build the strategy. A wrong strategy can lead your business to a bad situation. You do not want to attract wrong people but right people who can help you promote your business and endorse what you do. Your online community should talk about features, implementation and promotion.
Know your customers
Who are your customers? Where are your customers? Why do they need to come to your community? What will you provide to retain them? How do you respond when they are not happy? How would you moderate the community? You need to have clear answers for these questions. If do not you might spend a lots of money building a community with no plan. We hear lots of people say "We just need lots of people sign-up, then we can do anything". Sadly, people do not sign up for no reason. You should know your customers well.
Find a vendor
Leave it to the expert. You may have a team that can develop. But you need to find a vendor that has done it several times for several customers. Just by talking to an expert itself can give you lots of insight on your strategy. As an online community development partner we have helped several businesses succeed. You can not know every community software out there in the market but we work with most of the successful one. Selecting a community product can be a complex task as everyone says the things you like to here.