Basic question, but I want to enable page templates. I have one theme which has page templates enabled. I switched to another but there is no option to change the template, even when creating a new page. How do I switch this option on? I've had a root around on the Codex and forum but can't find it.
Chances are that the theme you've switched to has no page templates defined - they exist on a per theme basis.
Here's the Codex reference: http://codex.wordpress.org/Pages#Page_Templates