Switch Location Edit
The cruise control cancelling switch is located on the brake pedal arm adjacent to the separate brake light switch. On vehicles with a clutch, another switch will be located on the clutch pedal shaft.
Locating brake switches is pretty much the same process on practically every vehicle made. It's a simple process of locating a familiar landmark (the brake pedal itself) and following a well-marked trail (the arm that the pedal is mounted on) to the destination (the switch). As an example, watch this video of a brake light/cruise control switch being replaced on a Chevy Tahoe. Starting at 0:57, the guy says "So basically you got the brake pedal. Simply follow it up and there's the switch right there."
Switch Characteristics Edit
The switch has a two-wire connection that breaks continuity when the brake pedal is depressed. It also has a vacuum line connection. This vacuum line opens to the atmosphere when the brake pedal is depressed. The switch body threads into a swedged clip through a metal bracket rather than a properly threaded nut.