How to use categories and tags? (meta)

I’m thinking through how to use categories and tags on this blog … I know I won’t get it completely right the first time so it’s worth starting from the beginning tracking the different experiments I do.  Usefully, WordPress allows multiple categories as well as multiple tags, so one way of thinking about this is that I’ve got two different dimensions to label things in.  On top of that, I can use conventions to have (potentially-fuzzy) subdimensions, for example tagging each post as one or more of “personal”, “political”, “professional”, “entertainment”, and “meta”.  Or would those be better as categories?

Hmm, not sure.  So let’s use this thread to discuss.  References and citations, pointers to good/bad examples, anecdotes about good/bad experiences — using this or other technologies (e.g., Mediawiki categories) are all welcome.