I keep a handwritten log book of all my passwords and usernames, in a lockbox, out in the shed, which has a combination padlock, and the key to the lockbox is in the trunk of my car, in the garage, and the key to the garage is hidden under a big rock in the garden, which is guarded by a tiny attack Pomerainian, and a ferocious Chihuahua, that will nip your ankles to smitherines !
All my Trainz versions have the serial numbers, PW & UN writen down on a piece of masking tape, on the DVD case's, in a saferoom that has 3 deadbolts, with aluminum foil stapled to the walls floor and ceiling, and should anyone infiltrate my domain a trio of fierce black scratch Kats (with 4 wheel drive, studded snows) are ready to pounce on intruders ... and just in case, I have mousetraps set, and are rubber banded to all my DVD case's in a wall safe, hidden behind my picture frame of the Horseshoe curve, in my saferoom.
The safest place to hide anything is in the dishwasher, or in an empty box labeled Tampax up in the towel closet ... nobody will ever look in there