In mnemonics, you're constrained by how rigidly your brain insists on completing the usual pattern instead of doing something else. (It occurs to me that you could replace "mnemonics" with just about anything and preserve the truth value of the previous sentence. But it's especially clear-cut in mnemonics.) If you're trying to bind "camera" to "watermelon", it may be that the first thing that comes to mind is "camera takes a picture of the watermelon". It's natural to get stuck on that not-very-memorable image, going round and round with the query "camera watermelon?" and your brain's insistence upon the answer, "camera takes picture of watermelon". You say, "No brain, I need something else," and your brain is all, "Um, but that's what cameras do. How about... camera takes picture of watermelon?"
To reliably escape loops like that, it helps to have practiced the mental motion of trying out other possible interactions, and it helps to have a whole arsenal of them ready to go.
Here, I'll demonstrate. Camera and watermelon. Off the top of my head--really, I'm going to note the very first things that come to mind, like I would in real life:
- Yes, the camera could take a picture of the watermelon, thanks brain, keep thinking.
- The camera could transform into the watermelon, or melt over it, or deform to surround it, or absorb it, or bounce off of it. (Those count as one because they're my standard, not-really-trying interaction collection.)
- The water melon could eat the camera.
- It could tackle the camera.
- The camera could wrap its strap around the watermelon and strangle it, or make a noose and hang it, or drag it along on a leash. (All things to do with the strap, so that's one.)
- The camera and the watermelon could attempt to have sex, in which case they might spend the whole time looking for some configuration that would allow such a thing to happen despite their apparently incompatible anatomy.
- The watermelon could be fired out of the barrel of the camera.
- The watermelon could fall on the camera, crushing it and splattering its guts everywhere.
- The watermelon and the camera could tango, or waltz, or charleston, or do jumping jacks facing each other, or skip while holding hands, or race. (Those are all physical partner activities, so that's one.)
- The watermelon could spit seeds at the camera while the camera frantically dodges.
- The watermelon could vomit the camera.
- The camera could have a human-shaped body and a super power that lets it shoot watermelons out of its wrists the way Spider Man does with webs. (That was overly complicated, brain, but I appreciate the... whatever it is you just did to make that.)
- The camera could shit the watermelon.
- The watermelon could give birth to the camera.
- The watermelon could roll over the camera, squishing it and collecting it up like Katamari Damacy.
- The camera could make out with the watermelon.
- The camera could play tag with the water melon.
Finding things like this is quick and easy once you're used to it. I couldn't type nearly fast enough to get these down as quickly as I thought of them. (To be clear, I'm trying to give you evidence of your own potential, not to show off.) I've been at this long enough that I didn't have to stop for breath to make that list, and it ended because I didn't want to waste your time or use up too many ideas you might have if you tried this exercise. The watermelon would be finding ways to sharpen the camera's mechanical parts into various weapons by the time I was actually done.
It's slow and effortful, though, if you try to do it in real life without having practiced. And it's essential that this become easy for you, if you're after order of magnitude improvements to your internal memory.
Binding is the foundation of all palace-style mnemonics. Once you have a basic two-place relationship that isn't the normal expected thing, you can just feed that to your inner simulator and it'll start filling in all kinds of unexpected, emotionally potent details all on its own as you let the story play out.* With only the expected relationship, you have to make a separate effort to insert every single little detail required to boost the memorability.
There's no way mnemonic techniques will work fast enough to actually be useful if every time you cast out for something besides the usual pattern, your net comes back empty. You'll be stuck with the ordinary, boring, expected pattern. And there's nothing memorable about that.
*Incidentally, the PAO system for number memorization is a systematized application of this principle. "PAO" stands for "Person, Action, Object". To each number between 0 and 99, you assign a person, and action, and an object. Suppose 23 is John Luc Picard sipping a cup of Earl Grey tea, 45 is Captain Jack Harkness fucking a pterodactyl, and 83 is Barney the dinosaur eating a cake. To memorize any six digit number, you have the person from the first two digits do the action from the second two digits to the object in the third two digits. And you end up with "234,583" being encoded as "John Luc Picard fucking a cake". Now when you feed your brain a question like, "What does that sound like?" you don't have to do any extra work to come up with a memorable answer. Your inner simulator has something way outside of any of its usual patterns, and just about anything it could possibly supply for "the sound of Picard fucking a cake" is going to be highly memorable.
In other news, I've recently started offering private lessons in mnemonics, and it's going swimmingly so far. If you want to get good at this stuff super fast, I don't know of a better way than to work with me for an hour. Besides maybe working with me for three hours. I'm charging $100 to $200 an hour depending on the goal. You don't have to live in the Bay Area, because we all live in the future. Email me at email@example.com if you're interested.