Step 1: Decide what the post should do for you
Do you want to create business, get reposted/linked, have a call to action, or just start something?
Step 2: How can I be helpful?
Everyone wants to post something on their blogs to help others.
Step 3: The actual writing
You should let your message and intent guide your writing style/length.
Review last few weeks posts to prevent repetition.
These helpful tips were found at http://www.chrisbrogan.com/a-simple-blogging-formula/