I never played Quake 3 beyond the demo, despite playing Quake 2 (mostly Gloom and Action) for eight or so years, and later merely off and on, but interest in Quake Live and related subjects led me here. I obtained a CD/key, but I can't find what exactly I need to start playing. The in-game server browser is useless, and Planet Quake ain't what it used to be.

tl;dr What do I need to get/know to get Quake 3 ready to play?