1. Pick a position about a public issue, any public issue, that you are passionate about. Immigration. Digital rights management. Steroid use by athletes. Any issue you care about.
2. Make a case for something -- a position, an action, a policy -- related to this public issue. You don't have to prove your case, but you have to make it. It doesn't have to be an original position, but you need to go beyond quoting the positions of others. Provide an answer to your public's question: "What does the author of this blog post want me to know, believe, think, or do?"
3. Use links to back up or add persuasiveness to your case. Use links to build your argument. Use factual sources, statements by others that corroborate your assertions, instances that illustrate the point you want to make.