2. Ensure your pistol has a unique serial number, if not get it engraved
You can also get a serial number sticker from Customs that you can apply to your gun.
If you do this I suggest you visit the closest customs office with your guns, get the sticker, fill out the form and then put a clear coat to seal the sticker and prevent it from rubbing off. For pistols I put it on the underside just in from of the trigger guard and for Rifles on the mag well is good.