Here's some advice from expert bloggers on how to write a great blog:
Chris Garrett on 10 Key Ingredients of A Great Blog [1]
Tony Hung on the Rules Behind Creating A Great Blog [2]
Links:
[1] http://performancing.com/content/writing/10-key-ingredients-of-a-great-blog
[2] http://www.problogger.net/archives/2007/01/09/the-rules-behind-creating-a-great-blog/