What I know about commenting on blogs:
First you need to have a positive greeting. a positive comment that wont hurt their feelings. you have to have a question. to have no private information in the comment. after you did the greeting you have you make something thoughtful about the blog post. then you have to say something helpful that wont hurt peoples feelings and last you need to put a question. and now you done.
my first comment today is on roisin's blog