I am not an expert in marketing by any means, but I do know a little bit about SEO efforts, and the impact that blogging can have on your online presence.
The first goal with any blog, is to make sure that it is completely relevant to your goals, interesting enough to warrant being read, and most importantly, easy for search engines to identify a common theme. If you are simply creating a blog to help boost traffic, make sure that you are linking to various, high profile sources, giving your entry credit.
Another big part of blogging to remember is that content wins over style. Your blog can be the best looking blog around, but if you do not have the proper content to back up your style, then you will not benefit from your blogging efforts. For example, I am currently working on two different blogs for The Coho Oceanfront Lodge, a newly renovated hotel in Lincoln City, Oregon. I am using two different platforms to test the markets. First is my content site http://www.thecoholodge.com/blog.html. I focus on form and content more than I focus on style. Every month, this blog receives around 3,000 page views from search engine results, not generated from the hotel site, and has roughly only 1 - 2 posts. My style over content blog http://lincolncityoregonhotels.posterous.com/, is updated much more frequently with around 10 - 15 updates, and only receives around 500 page views.
What is the moral of the story? Just blog relevantly, giving your targeted user-base what they want to read. Do not put a bunch of time into style, as the content will be the spotlight.