The title, all in all. Do we need to start writing usage guidance and descriptions for the tags yet? This is needed in the future, but in the beta I'm not sure of. Ideas?
Yes! Explaining what the various tags are for is critical for a new site. Besides that, it also looks good when one goes to tag a question and sees that work has been put into the tag system.
Anybody can suggest tag wiki/excerpt edits. At the moment, we don't have any users able to approve them (it takes 750 rep to review tag edits during private beta), but that shouldn't stop anybody from getting a head start on filling in our tags. Besides, community managers will hopefully be around to work the queues that we can't yet handle.