I am trying to remote from a Windows 7 laptop and am using RealVNC Viewer on the Windows side to connect. I had read that the default Screen Sharing (System Preferences->Sharing->Screen Sharing) would enable the built-in VNC server but that didn’t work for me. Instead, I installed Vine Server (from http://www.testplant.com/support/downloads/vine/) – free, easy as a breeeze to set up and get to start at boot and connection worked first time!
I then built on that by setting the connection up in Guacamole so I access a web page served by Guacamole running on an Ubuntu 12.04 machine which itself connects to the Mac via VNC and the speed is actually pretty decent considering I am testing on the laptop on wireless. The idea is that I would be able to access the Mac via a web interface on my LAN from any machine without any additional software required.