Wired’s How-To Wiki has detail instructions on hot-wiring your – or someone else’s – car in a pinch.
The information is pretty straightforward and familiar: remove the cover, identify the starter wires, strip, zap. But with RFID blocks and mechanical theft systems in place you’re pretty much going to get zilch out of a modern vehicle. Use these only on your old Chevy Celebrity.
One important point?
This is illegal if you don’t own the car, so have your ID and registration (or some other proof of ownership) handy. If you are helping out a friend, that person must be able to prove ownership and must remain with you during the entire process.