Many people who have WordPress blogs give very little, if any, thought to search engine optimization (SEO) other than possibly setting the title , meta keywords, and meta description elements on their post pages.  But there are lots of things that can be done with a WordPress blog to optimize it for search engines. Also, many of the tips below apply to any blogging platform, not just WordPress.

Tip 1: Select an SEO-Friendly WordPress Theme
Tip 2: Dealing with SEO-Unfriendly WordPress Themes
Tip 3: Fixing URL Canonicalization for WordPress
Tip 4: Do Not Use Free Web Hosting
Tip 5: Host Your Blog on Apache
Tip 6: Custom Excerpts
Tip 7: Custom Title for Optimization
Tip 8: Custom Meta Descriptions for Optimization
Tip 9:  One Category Per Post
Tip 10: Noindex WordPress Archives and Tags Pages

See : http://goo.gl/LsrV7