To install X server from a minimal Debian install and make it start on boot: apt-get install xserver-xorg apt-get install fluxbox (for example) apt-get install xinit put "su -c /usr/bin/X11/startx " in your /etc/rc.local Make sure the user can start X. Therefor you might have to edit /etc/X11/Xwrapper.config and use: allowed_users=anybody
Untill today I thought managing startup processes and it's corresponding runlevels were a bit cumbersome. I used (well, I still actually) RedHat based distros, and they had the nice little utility called ntsysv. You can select what programs to run by means of a simple text gui. Thanks to Amoena's blog, I discovered sysv-rc-conf! Check it out!