Search engine optimize your blog's title tags. Mass edit the title tags of posts, pages, category pages, tag pages - indeed, any URL!
(If upgrading from a prior version of SEO Title Tag, be sure to deactivate the old version beforehand.)
Upload the seo-title-tag directory and the files within it to your wp-content/plugins directory.
Activate the plugin.
Configure the settings under Settings -> SEO Title Tag. You'll want specify a title tag for your home page which will override your blog name as the home page's title tag and specify a title tag for 404 error pages. You can also configure here whether you want all the rest of your site's title tags to have your blog name, or a shortened version of your blog name, or neither, appended to the end. IMPORTANT: You must save the settings, even if you haven't changed them from their defaults, in order to ensure that the title tags for Posts and for Pages works properly.
For those of you with a static Front Page chosen under Settings -> Reading, the "home page" described in the point above is actually the Posts page, and as such, the SEO Title Tag options page will actually will say "Posts Page" instead of "Home Page" - because it detects that you have selected a static Front Page. In such a scenario, in order to also customize the Front Page's title tag, specify a Title Tag on that page's Edit Page form, or within Tools -> Title Tags -> Pages.
Define custom title tags, meta descriptions, and slugs for your existing posts, static pages, category pages and tag pages in the admin under Tools -> Title Tags.
When writing a new post/page, define a title tag, meta description, and slug by typing something into the respective fields. If you're happy to use the defaults, then you can leave them blank.
To learn more about search engine optimizing your WordPress blog, you'll probably want to read Stephan Spencer's 10 tip series on Blog SEO (http://www.stephanspencer.com/blog/).