When you install docky, you'll notice that it tries to start up on any session if given a chance. If you attempt a guest session, then it will start up automatically. This is extremely annoying in Mint when the only panel in a default session is on the bottom - the same location that docky shows up, and thus it gets overlapped or covered by docky. This isn't a good presentation when you're trying to show Mint off to someone using a guest session!

The GUI to disable the automatic startup on login does not cause it to stop showing up on the guest session, whether when used on your account, or on the root account. I was frustrated with installing docky for this reason for a good while, but I finally managed to whip docky into submission, though I'm still not happy with the necessity of this solution. 

How to keep docky out of the guest session:

1) First, you'll need to become root for a moment. Don't worry, you don't have to log in as root, you just need to get the right folder open with root privilages. To do this, navigate to /etc/xdg/ and right click the autostart folder. Click "Open as administrator" and enter your password as required.

2) Now, in the file manager that opened with root privilages, look for a file named "docky.desktop". That's our troublemaker.

3) I recommend cutting this file out and pasting it into root's home folder if you're wary about deleting system files, thinking you may want to go and put it back again.
However, if you feel completely confident, you may delete the file instead of moving it.

4) Now close the root-privilaged file manager, and you should be good to go!

Test it out by opening a guest session with the indicator-applet-session panel applet (click "Guest Session" from its menu). Docky should not open this time!