There are cases when you can’t connect to a VNC server because it’s behind a NAT router (or some similar reason). Well, a cool trick you can use is to have the VNC server connect to the VNC viewer (which is set up in listener mode). This way, since the server initiates the connection, the NAT router can successfully pass the connections through.
To make this even simpler, you can generate a single-click VNC server using UltraVNC SC service. It’s a little tricky to use, but lifehacker explains it fairly well. Then you can just give the other person this .exe and have him/her double click it to set up the VNC session (make sure your computer is running the viewer in listener mode first though!).
This saves you either trying to run someone through router port forwarding (a complete horror) or doing the whole Hamachi + VNC thing.