It's easy to be vague in your community strategy:
“We’re going to approach males, aged 16 to 24, who love clubbing in London”
That might be specific for a marketing campaign, but it’s too vague for a community.
You should name specific people you will approach. You should justify why you're approaching them. You should know what you’re going to tell them (this means writing out the text or key points of your e-mail/call with them). You should know why they will listen (this should be based on their personal history).
This, naturally, involves a lot of research and thoroughly understanding the existing social ecosystem in which you will be launching your community.
For example, telling your intended audience to “join the community” isn’t going to work. Telling them about friends that have joined, some people you have in common, providing them with a unique opportunity based upon their unique interests is more likely to succeed.
Research might be fun to skip, but it's the quickest shortcut to a successful community. Do your research and be specific in your community development plans.