Various wiring options for a battery kill switch like this one.
IF THE IMAGE IS TOO SMALL, click it.
The "MAIN KILL" is best if you store the vehicle for long periods and want to keep the battery from draining, or to allow a trickle charger to work. The disadvantage is that all the memories (PCM adaptions, radio stations, clock) will be lost immediately. NEVER turn the switch off while the engine is running.
The "STARTER DISABLE" will allow the engine to continue running after it's switched OFF, but won't allow it to be started. This will preserve the clock & radio memories, and confuse most thieves since every other electrical device will work normally. It will appear that the starter is defective.
"ANTI-THEFT" is even more confusing since the memory circuits will continue to function normally, but the ignition switch will appear to be defective. This configuration doesn't require a heavy battery switch since the starter relay only needs a couple of amps to work. This also requires the switch ON for starting, and then it can be switched OFF while the engine is running.
Another option for the Anti-Theft setup is to transfer the Alt & FB feed to the same side of the kill switch as the fuse link, which is effectively the same as the Main Kill, but without the requirement for such a high-capacity switch.
Wal-Mart & some parts stores now sell a Chinese knock-off of the Hella switch linked above for about $10. It's not worth it.
This diagram was created from this set of symbols using MSPaint: