How I setup x11vnc on my Ubuntu 8.10 (intrepid ibex) laptop.
First I installed x11vnc via Synaptic (how to use Synaptic here).
Next in a terminal I ran x11vnc -storepasswd. It prompted me for a password (so I set a strong password) then it prompted me to verify by typing the password again.
After that it asked me if I wanted to write it to a file, I said yes.
Then I added an alias runvnc='x11vnc -usepw -forever' to my ~/.bashrc file to make it easier to launch. The -usepw switch causes it to use the password I setup earlier and the -forever switch causes x11vnc to keep running on the server side when you disconnect on the client side.
And finally, to launch x11vnc, I ran runvnc in a terminal.