Do you have a voltmeter? You made a good guess, but i always like to check. Worst case here though is you just don't get any power....

If you don't have a voltmeter or a test light, you can look at where the wires attach to the cigarette lighter. The very bottom is the hot (power) and the body is ground. You should be able to tell which wire is which.

As long as you have the switch wired up correctly and grounded, it will light up when you turn it on. But make sure the hot lead wire is capped.. you don't want that wire/lead grounded or you'll short it.