(1) X (at least the first xserver you run) usually runs on Alt+F7
(2) The depends on the startx script, almost all of them will look for a user startup script in ~/.xinitrc though. There is a (complex) example one here:
http://david.us-lot.org/linux-config.php (if you want it to do nothing but start the window manager then skip to the end of the file, you just need the exec line)