I added a Wiki for using LAX Shuttle C to reach In-N-Out Burgers
Effective May 2015, Parking Spot has implemented a customer-only policy for its shuttles at LAX. This effectively means In-N-Out Burger runs via Parking Spot Shuttle will come to an end.
From certain LAX terminals (e.g. T1), it is probably fastest to walk to In-N-Out Burger using the sidewalk on Sepulveda Blvd. This is a roughly 15 minutes walk.
From terminals further afield, you can utilize the free LAX Shuttle C to Long Term Parking Lot C. Take the Shuttle Bus at the LAX Shuttle & Airline Connections sign on the Lower/Arrival Level islands in front of each terminal. Exit the bus at the
first stop outside the airport @ 96th between Skyway and Sepulveda (before the bus enters the parking lot). From there, it is a 7~8 minute walk to In-N-Out on Sepulveda Blvd. See Google Map Here:
https://goo.gl/maps/yyuJu
To return to LAX, follow the same path back to 96th Street but continue past Skyway to the LAX Lot C Shuttle Depot to board awaiting bus. See Google Map Here:
https://goo.gl/maps/m4J3m