My rules are: Minimum 2 locks. All valuables or critical components removed from bike. If it's an ebike that means removing the battery and control unit if possible.

Multiple strategies.

For me, it goes like this:

• Two locks.
• removed the QR from my seatpost so that's not as easy to remove.
• I have a motion alarm hidden somewhere that isn't easy to see or access (i.e. can't easily break it off).
• I remove any accessories that are meant to be removed quickly, like lights. The mounts stay, but you'd have to unscrew them to get them off, and with the alarm, nobody is going to do this.

But I can expand this if my bike were needed to be left somewhere for prolonged periods of time (i.e. overnight):

• bike cover. Yes, this apparently can work really well.
• airtag or similar. This won't deter theft, so it's not on the top of my list, but may help to recover a stolen bike.
• replacing wheel QR skewers with the security type. I'm on the fence with this, because it would create convenience barriers with maintenance. This is why I prefer using locks to secure the wheels.

But the alarm + two locks already poses too many barriers for someone, and the likelihood is that they'll just target someone else's bike.