I ran across this gem just the other day and I have been working with Linux for years now. I know I will get a lot of use out of this command. If you would like to know the full executable path for a program in Linux, if you issue the following command in a terminal window, it returns the full path of the program executable.
which [program name]
So for example, if you are looking for the location of the guake terminal executable, the following screenshot shows the results from a Ubuntu platform.
This is definitely going to come in handy with startup programs. See the post on Gnome 3 startup applications for information on getting to the startup programs on the Gnome 3 desktop.