"Setting up a blog" seems like a vacuous idea, with all due respect. You set up the blog because either 1) you have something to say 2) you've discovered a sure-fire Google-ad niche. Build from there. The blog is the means rather than the end (taking on a preachy voice).
I run and help on a number. One of the easiest pieces of advice is to use Blogger.com. If you're focusing on a specific subject, you'll find yourself in Google molto quickly.
Try and stay topical. Visit other relevant sites and leave relevant comments. Address the issues of the day. Every time you link to a site, inform them. Every time someone contacts you or comments, reply. You will start to find yourself on their PR mailing lists and can become a source of info. However, note that if you go this route, you will have to understand the basics of journalism in terms of giving balanced views, checking facts, etc.
Some of the most popular blogs are "outspoken". People in general like to hear your voice in your writing. But unless you're trying to become an outrageous editorialist, anchor your comments in reality.
I run a blog on European screenwriting.
Screenplay Europe Although the actual readership is quite low, it has brought me into contact with lots of people and led to me being invited to sit on the jury of a movie festival. It also helps when I attend festivals, etc. These are very real offline benefits of online activity. The tone on this blog is deliberately neutral, as it provides news rather than reviews. It all depends on why you're blogging in the first place.