How do you del.icio.us?

del.icio.us strikes me as a great concept, but I just can’t get a grip on how best to use it. I have a functional, regularly trimmed set of bookmarks for Firefox (I don’t really use IE much) which serves me fine. Some people seem to store a hell of a lot of stuff on del.icio.us, which can’t possibly be reflective of their bookmarks in general.
What I’m looking for is suggestions on how best to leverage the power of del.icio.us. Hit me.