I wanted my homepage title to reveal my writing goals and interests. The importance of the title, to me, is obvious:

• It’s one of the first things people notice.
• It’s visible in the window chrome, the tabs, the bookmarks
• It’s something search engines pay attention to

WordPress settings allow you to set the blog title and description. With this modification, the description will be appended whenever a post title is not displayed, to avoid making it extremely long.

Edit the functions.php file of your template and append:

add_filter('wp_title', 'dv_wp_title', 100, 3);

$dv_append_subtitle = false;

function dv_wp_title($title)
{
  global $dv_append_subtitle;

  if($title === '')
    $dv_append_subtitle = true;

  return $title;
}

function dv_the_subtitle($sep = '—')
{
  global $dv_append_subtitle;

  if($dv_append_subtitle)
  {
    echo $sep ? $sep . ' ' : '';
    bloginfo('description');
  }
}

Then go to header.php and make your title tag look like this (notice that I added the dv_the_subtitle call)

And that’s it! If you want to customize the separator, which defaults to — pass it as an argument to dv_the_subtitle.