From Lizzie:

Personas:
http://www.naima.com/community/ch03/index.html

Think of say five imaginary future community members and outline their:

Name
Age
Pick a photo to represent them
What they do (a) in real life (b) online
Their 'back story'
Their friends
Where they live
What equipment they have
what they do
What would trigger them emotionally to engage, interact, convert from a lurker to an engager

Then you use these for your UI design and also for you community management and roll out plan

Pick either the people you hope to attract or the people you think will come

http://www.naima.com/community/ch01/building.html#understand