Over at ZDNet Dion Hinchcliffe has written a very good and comprehensive list of important things marketeers should pay attention to when starting a community, or even when they are already running it.
Below is a quick run down of his points, as well as my added thoughts. For the entire article you can visit this [...]

It’s easy to set up an online community. Buy some hosting, pick the tool of your liking and without too much effort you should have set up a ‘community’ in no time.
However, just because you call it a community (or the software vendor does!) doesn’t make it a community. What you have done so far, [...]