To help out the many people we’ve converted from Windows to Linux over the last couple of years, we use a closed source commercial software program called TeamViewer
TeamViewer is a Windows software package, however they offer a Linux version that has its own, built in WINE wrapper to run under your Ubuntu based distribution.
While this is commercial software, they are happy to let you use it for free for noncommercial purposes. They do however have an annoying nag screen on the host computer after you disconnect.
One nice feature of TeamViewer, is that each session creates a unique password, so when you’re doing phone support, after instructing the person being helped to launch the software, they then will have to give you the password for that session. Yes you can set a permanent password if you wish, but I find most people appreciate the fact that I can’t get in whenever I want, only when they allow it.
TeamViewer uses HTTP port 80, so no further configuration is required once the software is installed and launched. Using SSH or VNC software would require ports being opened in your friend’s firewall to allow access to their computer.
I must add, that in 2 years of converting people over to Linux Mint from Windows XP, I’ve only had to use the software a couple of times. Mint is so intuitive that most questions are solved in a 1 minute phone call. In one case a neighbor had a weird problem. She has an HP computer, with a known video card issue that would cause the cursor to disappear after a time. Installing the Nvidia drivers for her solved the problem.
So if you want to get friends to run Linux, and give them some piece of mind about it. Then install TeamViewer after you get their machine set up for Linux.