According to the patent application, Google’s Blog Search uses two main criteria to determine how a post gets ranked:
1) A blog quality score, which measures the quality of the entire blog based on factors like feed subscriptions, incoming blogroll links, PageRank of the blogs and other usual factors used for regular pages.
2) A post quality score, which measures the quality of the individual post by measuring the frequency and relevancy of keywords, among other factors.
So what can you do to make your blog more searchable (aside from writing nice, keyworded post titles)? Here’s the rundown on the positive and negative factors Google Blog Search uses written by SEO By The Sea, who kindly decoded the patent application’s tech-speak [en español aquí por TechTear] :
popularity of the blog,
Implied popularity of the blog,
Inclusion of the blog in blogrolls,
Existence of the blog in high quality blogrolls,
tagging of the blog,
References to the blog by other sources,
A PageRank of the blog, and;
Other indicators could also be used.
Frequency of new posts,
Content of the posts,
Size of the posts,
Link distribution of the blog,
The presence of ads in the blog, and;
Other indicators may also be used.
Check out the SEO By The Sea post for more details on each of those factors.