There was a great anecdote (or perhaps an urban legend). Back when Mir space station was still operational, one of its crews lost something. What it was exactly doesn't matter, but they looked everywhere. Twice, and then some. Out of utter desperation and puzzled beyond belief they started peeling off parts of the cabin walls and looking underneath. And what do you know - under one panel there was a folded piece of paper that said "It is not here. We already looked." Signed by another crew from a year ago. Apparently they also lost something, but were thoughtful enough to leave a note.
So, yeah, notes are great... even if not terribly useful :)
I do the same for "accessories" - for e.g if I buy a desk and assemble it - I then take a zip-lock bag, put in the wrenches, extra screws, fasteners, what-have-you, and tape it to the desk where you can't see it (usually on the back, or bottom if possible).
I do this for almost everything I own - I even tape the instruction manuals to the back of appliances.
This way, I don't have random items floating around the apartment, and I know if I need to fix, replace, or dissemble anything, I know I don't have to hunt around.
I guess this is an extension of jgrahamc's idea - take pictures as you assemble, fix, dismantle stuff, and put them in the zip-lock bag. Saved me endless head-scratching in the past.
Heh, I do the exact same thing. Especially with Ikea furniture - I would tape the wrenches, manuals, etc somewhere not easily noticeable.
Another thing I do is behind my TV, or in the back of my computer, I create little paper tags that I tape onto the power cables. So, in case I need to unplug something from the wall, I don't need to trace the connection to know if I'm going to unplug the TV and lose all my presets, or just the floor lamp.
This seems like a brilliant use case for augmented reality. If I could look at something and have my HUD display "turn this valve to disable all water flow to the upstairs" from the previous owner of my house (or from the contractor who plumbed the house, though who am I kidding?), that would be really cool.
I seem to remember another car manufacturer planning to make a mobile owner's manual where you hold up your phone in front of the offending car part (e.g. the gear shifter) and it pulls up information about it.
If you do this, and you should, then please do it with a permanent marker as opposed to pencil or biro. In 10 years it will not fade away leaving a tantalising tag with no information.
I've done this (read: had to do this to save my sanity) for years now. Learnings: Most inks (like inkjet printers, pen inks, and even pencils) fade (esp if in light for extended time) and laser toner will stick to other surfaces in heat, so like another poster mentioned, sharpie perm marker is usually the best option. Yellow sticky notes do not stick after years, sadly. Duct tape is great, electrical tape often gets gummy and peels (at least, the cheap kind I buy).
I'm a fountain pen fanatic, mostly because they are awesome to write with and improve your handwriting. One of the perks is that you can use archival grade ink.
My favorite are Noodler's Inks (http://noodlersink.com/). Forgive their 1995-esque website, they make fantastic fountain pen ink. Their Bulletproof line is not only archival quality, but also nigh-impossible to remove from paper.
And their Heart of Darkness black ink is like peering into the very abyss itself.
Very true. Conversely, the water-based "won't stain your clothing" ink fades very quickly, which is pretty bad for archiving. Perhaps you can guess which one I used when I "commented" things around my house a few years ago.
So, yeah, notes are great... even if not terribly useful :)