How do I change gallery titles? Say, I'm using the default theme.

The Gallery title is changed in the config.php
not sure if you actually wanted album titles or not but that is actually a good question. You could just rename the folder and it will rename the album but it will leave alot of junk in the db.. maybe there is a better way.. ?????Good question

If you do mean album titles, just go to the admin edit screen... click "edit all albums" and you can edit titles and descriptions.

ummm.. oh yeah..