Adding blog entries to the website gives the search engines new content and keywords to interpret.
Just like a traditional page, the structure of your blog entry is important. Think about the title tag, headings, alt tags, etc..
When blogging or writing articles be on topic 20% of the time and more general the other 80% of the time.
The internet is filled with general articles about everything. Be as specific and unique as possible to drive searches to your site.
Create an editorial calendar to help keep you on track. Many people start blogging and after the initial excitement they stop.