Initially, understanding why we forget things is the best way of finding out how to remember something in the first place.
To remember something important, information needs to encode on a deeper level. Give the brain a hint that the action done is essential, and memory will encode with a higher success rate. Above all, pay attention to what needs to be remembered. Create a vivid story where, at least for a brief moment, you can imagine an interaction of components, making sure to give the mind a fair chance to encode and store needed information into the long term memory.
Isn't it strange that it can be so hard sometimes with the idea of how to remember something? We have these remarkable brains made up of billions of neurons that can complete complicated tasks like moving all the body's muscles in unison to get up of the bed with no effort at all. Yet we way too often come home from the grocery store without the bread, walk into another room and forget why, or forget names and fail exams. What's up with that?
Well, it all has its explanations, and when you know about these, you can use them to your advantage. There might not be a single best way to remember things especially, when it comes to striving in recollections on how to remember where you lost something. Initially, understanding why we forget things is the best way of finding out how to remember them in the first place.
Probably the most common reason for forgetting something is that you never really applied various ways to remember things in the first place. You might have thought about it, but that doesn't mean that you committed it to memory. Well you might think then on how to remember where you put something you lost. Seems like impossible wordplay. The reason for this is the handy little mechanism known as the working memory. Think of this as your memory's head-up display. Whatever you have on your display is what you can currently work with. This is limited to just a handful of things, which means that if you try to think of too many pieces of information at once, some of them will actually "fall out" of your working memory frame.
So when, for example, you are going to the kitchen to see if there is any soy milk left and find yourself opening the door to the fridge and having no idea about what you were going to do, it is very natural. You probably started thinking about what to watch on tv this evening when you passed the living room, and this was enough to push your soy milk thought straight out of the frame.
But not all the thoughts entering the working memory are so short-lived. For a few lucky ones, the golden gate leading further to the long-term memory suddenly opens. If they manage to take the leap from short term memory, they can be sure to stay for at least a big while longer. However, for the brain to decide to let something enter its long-term memory, it has to be important. So if you want this to happen, YOU have to give your brain a hint about the best way to remember things.
A typical example of when you don't do this:
YOU: *I am arriving home and really have to go to the toilet, so I quickly remove my jacket and put my keys on the kitchen table on my way there.*
YOUR BRAIN: *Important right now: Have to pee. Not important: Where I put my keys.*
You likely didn't even think about where you put your keys but did it mainly on reflex. This means that the thought of the keys on your kitchen table might not even have entered your WORKING MEMORY. Then it, of course, had no chance whatsoever of reaching the hall-of-fame of the long-term memory, a spot where it’s easier to remember these things for future reference.
YOU: *I am arriving home and really have to go to the toilet, but first I put my keys on the table where I can find them later. It is said to give bad luck, but I don't care about it now because I really have to pee.*
YOUR BRAIN: *Aha, this key thing seems to be quite a big deal, welcome to the long-term memory! I still have to pee though.* Now it will be easy to remember where the keys were left; you placed them there intentionally!
So when you panic and think on how to remember where you put something you lost, like your keys, check around, maybe this time, you made plans ahead!
So the first key here is paying attention to what you want to remember.
The second thing is to connect the thought to something else.
If you think of your memories as a huge web of interconnected bits and pieces, it makes sense that to extend this web, you have to connect the new information to threads already in it. Creating those crucial ways to remember things.
That's why it helps thinking about the superstition idea of keys on the table. It creates a further connection between something already in your long-term memory and the new knowledge of where your keys are currently located.
If you want to be absolutely sure of remembering where you put your keys (and approach the realms of the memory masters), you should aim for making not only one but several connections between the new memory and those you already have in your head. So that instead of just hanging onto a loose thread at the end of the big web, the info is heavily entangled in it. Process of how to remember where you lost something simply becomes stuck in the traceable web of ideas. Can clearly see it stuck in that web, look again!
Since there aren't that many great connections between a pair of keys and a kitchen table, you can simply make up one. This alone unravels into what is a mnemonic device! Technique to remember things, here, let's say that you briefly imagine that your key becomes huge and rattles and spins like a chain-saw and that you use this chain-saw key to cut your table in halves. Then you suddenly have created a ton of associations between your keys and your table: The vision of the key shredding the table surface; The hereafter hostile relationship between the keys and the table; The magnitude of your mighty keys in contrast to the kitchen lamp, etc.
And what's more, these associations are unusually strong thanks to the unusualness of the whole event. Of course, it didn't actually happen, but so what? It happened in your mind, and to your brain, that is almost the same thing. So it will register this memory as something very important to keep in the long-term memory. (So that you don't go around accidentally sawing other people's tables apart as well!)
This may at first sound like a crazy and complicated way of remembering something very simple. Still, after some practice, it becomes second nature, and it will save you many frustrating hours of searching the whole apartment for keys. Above all, it forces you to pay attention to what you want to remember. To create such a story, you have to, at least for a brief moment, really think about the components of it, and that makes sure to give you a fair chance of remembering them later.