I struggled to connect to the console of a newly created VM. The VM was created using Oracle VM Manager (OVMM) and despite efforts to install the required packages I could not use the console button in the Manager interface.
I noticed that the VNC server built into the VM was listening on 127.0.0.1 only (on the OVM server), you can see this if you check the file vm.cfg for the guest. Without analysing how the OVMM would try to connect to the VNC server on the other host I decided to create an ssh tunnel from my Mac to the OVM server:
ssh -L 5901:localhost:5901 firstname.lastname@example.org
(replace fu.bar.com with IP address or host name of your OVM server).
Now, I think I have found a reason why Oracle specifically recommends TightVNC as a VNC viewer; I tried two other VNC viewers on my Mac, but I could not make them work with the console on the VM, sometimes it connected, but later it would hang, another just aborted. I downloaded the java version of the VNC viewer from http://www.tightvnc.com/download.php and connected without any problems to localhost and port 5901 (using the tunnel created above).