How you disable the lock varies a bit from vehicle to vehicle but genrally you remove the steering wheel, inspect the lock and see if it is even possible to disable it. Some if you do so you will not be able to start it.
I recommend a multi-step approach.
1: Leave key in it
2: install hidden "Ignition disable" switch
NOTE: on many vehicles you have to pull a fuse when towing, Wire this circuit through the same switch (if, that is the fuse you pull is not the one you need) so you basiclly have a DP-ST switch, on for driving, off for towing, both pulls the fuse and disables the starter/ignition.
Match the color of the switch to the spot it's mounted and by the time Mr. Auto-Thief finds it,,, he will be a guest of the local constabulary.
Home is where I park it!