Just like the city does with its parking enforcement.
McDonald's used to use chalk on a tire, but nowadays, there is a Smartphone app that will read license plates, and record the car time. The next time they do the scan of the lot, the app knows who has parked longer than allowed, and calls the tow trucks. McDonald's get a small part of the towing fee, but their goal is to have parking for customers, the tow trucks though, they make some serious money on their scheduled "routes".
Just don't do it, pay for parking, or find a true free parking for all, such as a city run lot, as I mentioned I use the Public Library area near City Hall. The Fullerton Train Station is another good choice, and the Bravo Route 543 bus has a stop there. ARTIC is also available, but then the Route 50 bus stops at Harbor and Katella, and then you need to walk a few blocks.
Do not park in a Shopping Center, even though they don't tow that often (usually), they do have the right as they are private property.
Also look at Carpool commuter lots, the LA Metro Route 460 stops at the Fullerton Park and Ride Lot off the 91 freeway near the 5 freeway.