Local web dev in OSX

I know how to design a website. What I don’t know how to do is to test one locally—properly, that is (file:// doesn't count). I’m moving two of my sites off Tumblr to publish with Statamic. It’s a flat file CMS, no database. Needs Apache and PHP, that’s it.

Unlike my days with Movable Type, Wordpress, and Tumblr, I’d prefer not to test changes on a live theme because the tempting language doesn’t work locally. So what are your suggestions on local web development best practices? I’m running Mountain Lion and I don’t know the difference between .dev and .site. Yet.