General reference: http://en.opensuse.org/Remote_Access_to_SUSE
This config is handy but unsecure, use it only if needed. NX is much more secure and should be prefered.
I sometime needs graphical remote access to my server, even if it's not so often.
First, and this is probably the main thing, go to yast and setup remote administration.
My server can run xfce, but default VNC is twm.
Installing VNC, using YaST remote access makes all the VNC setup. Then one have to launch manually "vncserver", give (only the first time) a good passwd (stored in .vnc/passwd) and look at the answer to know what is the display number.
netstat -ta (as root) allows to verify that ports 590x and 580x are listenned to by VNC (x is the display number, 590x for VNC itself, 580x for the java web version).
On the client, "vncviewer IP:display number" gives access. For example "vncviewer dodin.org:5".