How to teach blogging to kids....

Slade School have asked me to do a session on blogging for an IT group of children. Do I know anything? Come to think of it, I've never really tried to analyse it before now. I just sort of start writing and either vent my spleen or say something funny, depending on what mood I'm in. Keep it short and funny and eye-catching is my first thought by way of advice. But do I even take heed of my own advice? Why do I want to teach an army of school kids to enter this murky world we call the blogosphere?! I'll do my best for them!...