how to find the seo of a wordpress theme?

[Jake]

Search Engine Optimization, involves in part making your site more search engine spider friendly, so their software robots can more readily identify your site's content.

Here's a Google on site SEO guide that shows some of the things an SEO optimized theme attempts to accomplish.
http://www.google.com/webmasters/docs/se...-guide.pdf

On site SEO also involves how the content is organized, some themes may order the source code better for the search spiders, add fields for a meta description to be typed in and add 'related' or next/prev post links on pages.

There are plugins like the well know All In One SEO plugin that adds meta data to any WP theme, that particular plugin is said to be a heavy processor load due to the brute force method used to rewrite the page.