I’ll cut to the chase: put things where you’re likely to find them later. If you want to remember to drop a letter in the mailbox in the morning, put it on your dining table the evening before so you’ll see it on your way out. If you want to stop losing your keys, decide on a place in your home where you’ll always place them; it could be a hook next to the door or a bowl on a side table. What matters is that you know where they’ll be there when you need them.
As Annie Murphy Paul explains in her book The Extended Mind, your environment is part of your cognitive apparatus. The bowl isn’t just a physical container for the keys; it’s also a mnemonic that keeps you from going nuts on the way out of the house.
Interestingly, “out of sight, out of mind” also applies to stuff you want to keep out of sight for now — i.e., in longer-term storage. For example, I have a case for camera gear such as lenses, batteries, etc. I don’t use them often, but I know where to look for them. You may have similar containers dedicated to specific kinds of things in your home. If you’re like me, you’ve developed a gut-level awareness of where things are stored. So when a new one of “those” comes into your life, you know just where it goes.
The challenge is that some things aren’t easy to categorize upfront. It may be the first one of “those” that comes into your life or it might be something that straddles two or more categories. Where should you put it? It sounds facile to say, “put it where you’ll find it later.” How do you know where that is? Where will “future you” be likely to look for this thing? It’s not an easy decision since what makes logical sense to you now might not make sense in a month.
I’ve learned to go with my gut. Whenever I think, “where should I store this?” some place usually pops to mind immediately. Sometimes it’s a surprising location that doesn’t make logical sense — but it feels right. My sense is that if this is where “present me” thinks this thing is supposed to go, “future me” will assume the same. So far, this approach hasn’t let me down. Conversely, whenever I overthink storage by creating elaborate top-town organization schemes, I misplace things.
Bottom line: how you organize personal stuff doesn’t need to make sense to anybody but you. (This principle is obviously moot if you’re in a collaborative situation. E.g., my wife and I jointly agreed where to keep the car keys.) By the way, “go with what feels right” also applies to storing digital stuff. The stakes are a bit lower since often search will bail you out, but it’s good practice to stay organized. And I can’t do it for you; the best personal storage scheme is one that makes sense to you.