Matt
Cutts suggested that it is best for your to try to anticipate what the
user will search for when crafting your title tags. When you do that
and then when it matches the query, then Google will likely show your
title tag. Google uses three criteria when determining if they should use your title tag:
(1) Something that is "relatively" short
(2) Have a good description of the page and "ideally": the site that the page is on.
(3) And that it is re
levant to the query.
If you fail on these criteria, then Google may use (1) content on your page, (2) anchor text links pointing to the page and/or (3) may also use the Open Directory Project.