Starting sessions, registering variables, destroying sessions with global_variables off....

I just switched from a 4.06 server with global_variables ON to a 4.22 with global_variables OFF.... Can someone give me a quick run down of how to set/unset variables and register/destroy sessions with PHP 4.22 (global_variables OFF). I've been all through the php.net manual and still can't figure it out. I know that I have to use $_SESSION['foo'] instead of just $foo now, but for some reason I can't get session_start(); to properly start a session. Any ideas?? Thanks!!