There are a lot of different types of sites within Web2.0 - the social news sites like Digg/Fetch/Mixx/Propeller etc. 

The social networking sites like Facebook/LinkedIn and

Social bookmarking sites like Del.ic.ious/Mag.nolia. 

All of them take different strategies and tactics since they are very different sites.  The one thing they all have in common however, is they require good content from YOU to be effective.   

Even the networking sites need for you to flush out profiles and contribute good info so when you join groups and "mingle" you'll attract leads and interest.

 This is a very good article on Web2.0 strategies... http://www.infotoday.com/mls/mar07/Fichter.shtml

 Good luck!