use of robots.txt make sure content is only crawlable and indexable in one URL location
use of nofollow in comments, yes you might get more comments with dofollow
URL method: WordPress comes with several built in search optimization tools, including the ability to use .htaccess to create apparently static URLs called permalinks.
Sitemap: Creating a Google sitemap for your blog is a easy process.
WordPress SEO Plugin - Plugin optimizes titles, meta tag information and RSS link feeds for auto discovery.
Title Tags Change: Changing a post’s title tag you need to install SEO Title Tag WordPress Plugin. SEO Title Tag lets you define custom page titles for your posts.
Optimize images : Images can open up a whole new stream of search engine visitors for your blog.
Optimize links : Links are one of the most important factors that determine your page’s value in a search engine’s eye. Knowing how you should link to internal and external pages will improve your rankings a lot.