Cart before the horse?

Started first student blog. We'll do a test first, just to see if everyone can post successfully. Next week we'll take off with a real assignment. But now I'm reading some blogs about blogs, with some good guidelines/rules for students. I haven't really given my students guidelines, though I did tell them that what they write will be public, and that comments on the current posts, if they choose to add them, should be positive. I'm not too concerned about inappropriateness. But I will think about whether I should put some guidelines in writing.

Another thing: a rubric for grading posts? Might be a good idea. I have an example of one for biology that might give me some ideas.