[Plugin: WordPress SEO by Yoast] Change Title Template Variables

In the admin when you’re editing page titles, you can use variables like this: %%title%% %%page%% %%sep%% %%sitename%%. It would make things a lot cleaner and easier on the code side to change that instead to :title :page :sep :sitename. Then, when replacing it, you just use strtr:

$title = strtr($title, array(
    ':title'    => $post_title,
    ':page'     => $page_number,
    ':sep'      => $separator,
    ':sitename' => $sitename,
    // etc...
));

http://wordpress.org/extend/plugins/wordpress-seo/