Courtesy of our friend Andrew Westin, AKA The Food Monster:
These guys are all about creativity when it comes to the Ghetto Big Mac. Remember, the McDonalds employees are there to serve you, so small requests should be granted. I have found this to be true across the board.
Ghetto Big Mac
Double cheese burger, small fries (value menu)
Ask for Seeded Bun, Big Mac Sauce, and large cut sliver onions.
(Thanks to Andrew for the submission!)