on a older vehicle, the best way to hotwire is jamming a screwdriver in the ignition switch and changing the switch position with the screw driver. Or you just hammer a flathead screw driver into the key cylinder until the lock break. On older GM cars the ignition key cylinder is attached to a linkage that mechanically moves an ignition switch like this:
(usually mounted on/near the firewall)
And if you jack the steering wheel to one side hard enough you can break the wheel lock (so you can steer)