What I think you are asking for is how to get the Window managers up and running.
This depends whether you are stuck at the boot loader or if Debian boots but you don't get a graphical interface to work with.
If Debian boot alright you should see lots of lines telling you what services that start. If this is the case there is nothing wrong with Debian (otherwise look further down), what you see actually is the OS ( I know it doesn't look much
). What you have to do is log in as super user (root) and then check
Near the top there should be a line similar to
That line tells Linux what runlevel to start in i.e Single user, Multi User, X11.
If there is a '3' instead of the '5' that means you are starting in non graphical multiuser mode. Change that to a '5' and reboot.
If you have a '5' in the line you have some trouble with your X-window system. Log in as a normal user and type 'startx', 'xstart', 'xinit' that is different on every distro, check if you get any errors that might help you.
if you don't boot into the os you have problem with your boot loader, grub or LILO. Check what debian uses and google for it.