Ever since I was a kid, the way I remember which one is “vertical” and which one is “horizontal” is by singing to myself a line from the Olivia Newton-John song “Physical”
I started this when I first took geometry in the 80s, and still do it to this day.
Does anyone else have any weird mnemonic devices that help them remember stuff that may be unique to themselves?
Well, the horizon is horizontal.
There are tons more I’ll remember later.
The gas cap is on the opposite side of my car as my wife’s car. I was forever pulling up to the wrong side of the gas pump until I finally figured out this mnemonic:
On my car the gas cap is on MY side (driver side), on her car the gas cap is on HER side (passenger). It helps that I almost always drive when we are together, regardless of which vehicle we take.
Bad boys rape our young girls, but violet gives willingly (resistor color codes)
Not that I’d recommend that one - just remember it (but don’t need it)
I’m sure it’s not unique, but I did come up with it on my own when I was a tyke. “Port” has the same number of letters as “left”, and “starbord”, uh, must be the other one then (right).
Most (newish) cars have a little arrow on the gas gauge indicating which side the cap is on.
I remember that one. IIRC, they also would add Get Some Now for the tolerance bands (gold, silver, none). I had teachers vaguely refer to it, as in there’s a mnemonic device we WILL NOT be using.
Those are pretty standard. I think the OP is looking for mnemonics that people have come up with personally that are odd enough that it’s unlikely anyone else uses them, let alone teaches them to other people.
For example, I have a historical timeline in my head that is keyed to Billy Joel’s “We Didn’t Start the Fire”, just because the song randomly seared itself into my memory when I first heard it.
Missed the “unique” part.
While I have heard the righty-tighty thing before - I never needed it - as when I was in middle school - I had a teacher say (when I was asking which way to turn a bolt):
“Just remember - counterclockwise - always - to loosen”
I have no idea why - and it sucks as a mnemonic device in the traditional sense - but that always stuck with me and have never forgotten it.
I don’t have many devices, but one that I learned for a test - and to the best of my knowledge have never used since is: “SPA” for the chronological order of Socrates, Plato, and Aristotle…
I tried this one, but kept forgetting whether it Port was left because it had the same number of letters, or Port was right because it didn’t.
A workmate recently told me a much easier one: “I have a little port left in my glass” - from this, you can get both the side and the colour of the navigation lights - port is left, port wine is red.
Every acid dealer gets busted eventually
Open guitar string notes in standard tuning.
Not really a mnemonic…but the backslash is just below the backspace key on most keyboards. That has been a revelation to many people that I’ve taught it to over the years.
“Please Come Over For Gay Sex”
Phylum, Class, Order, Family, Genus, Species
There are some other great ones (“Pickles Please Mellissa Carnally”) but I don’t remember them off the top of my head.
I used to misspell “significant” until my wife reminded me to think “Sign if I can’t”
If by ‘most’, you mean ‘in the USA’.
On my 97 Contour, the gas pump pictogram is on the right, with the nozzle on the right of the pictogram. On that car, the gas cap is on the right, and I’ve heard the claim that that’s fairly common, to have either of those elements (if not both) on the side that matches the gas cap.
I use the “tap the knuckles” method of remembering which months have 30 days vs. 31, and learned a way to do multiples of 9 on my fingers (count from the left, fold down the finger corresponding to what you’re multiplying by, the tens place of the result is to the left of the folded finger, the ones place on the right). I still have to think about 7s and 8s, though (blame a month of hospitalization at the wrong point in third grade).
Thanks for this.
I came up with one just the other day. For no reason whatsoever I wanted to remember the left-to-right orientation of the presidents on Mt. Rushmore.
I settled on Would Jesus Rake Leaves?
Washington, Jefferson, Roosevelt, Lincoln.
mmm
I like that one. I always heard something like “when sailing, the port should be left behind.” Of course, many may disagree with this practice, causing some confusion 
Another spelling mnemonic, this time for “Connecticut”: Picture a telephone lineman yelling to another lineman, “You connect, I cut!”
There’s a gazillion mnemonics I’ve used. Probably the weirdest is for the first stages of prophase in meiosis (from an old thread on the same subject): Leaping Zebras Pounce Down Drains, for Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis. There’s probably something useful I don’t remember because of this tidbit that’s stuck in my brain for over 30 years.
There’s another mnemonic I remember, but damned if I can remember what it’s for: Egad My Tiger Has Cancer.
I could never remember whether it was Tiger Wood or Tiger Woods (and needed to, because I was writing crossword clues at the time) until I realized he has the same number of letters in his first and last names – Tiger Woods.