TaleraRis (and others) said:
I learned this as: Kindly Pay Cash Or Find Good Substitute.
Pretty boring, but I still use it.
um, lets see her, just a few EMT’s use
A - airway
B - breathing
C - circulation
P - pain
Q - quality
R - radiation
S - severe
T - time of onset
A - allergies
M - medications
P - pain
L - last oral intake
E - events leading up to
C - chief compliant
H - history
A - assessment
R - treatment(rx)
T - transport
Ahh… just round to 3, it’s close enough 
OTOH, if you really need more digits… and if I can recall it correctly… PI to 20 places:
Sir, I bear a rhyme excelling
in mystic force and magic spelling
celestial spirits elucidate
all my own telling can’t relate.
Que j’aime à faire apprendre un nombre utile aux sages!
Immortel Archimède, artiste ingénieur,
Qui de ton jugement peut priser la valeur?
Pour moi, ton problème eut de pareils avantages.
…count up the letters in each word (remember that j’aime is two words).
Okay, it’s not really a mnemonic, but I use the knuckles on my hand to remember which months have 31 days. Here goes:
Curl your hands into two fists, and put your hands together, back of your hands toward your face. You should be looking at the “bumps” and “valleys” where your fingers meet the hand. Okay.
January has 31, so it’s the bump of your left pinky.
February has 28, so it’s the little valley between your left pinky and left ring finger.
March has 31, so it’s the bump of your left ring finger.
April has 30, so it’s the next valley, and so forth.
Just alternate valleys and bumps counting by the months. July and August both have 31 days, so they’ll be the bumps of both your pointy fingers.
Trust me, it works.
For the OSI model:
A
Particularly
Simple
Type of
Network
Design
PLEASE!
It does, but it seems a lot more complicated than just memorizing “30 days has September, April, June and November–all the rest have 31, except for February, blah blah blah”
Wow- however did I miss this thread?
My mnemonic for remembering the resistor color code:
Bad Boys Rape Our Young Girls But Violet Gives Willingly.
For the OSI reference model (from the bottom up):
Please Do Not Throw Sausage Pizza Away.
And for remembering vector relationships between current and voltage in inductive & capacitive circuits (this one is complicated; hang on tight):
ELI the ICE man: (supposedly a well known song from a thousand years ago, but it works for me anyway). Where E represents voltage, I represents current, L stands for an inductive circuit and C for a capacitive circuit. Hence: ELI means in an inductive circuit the voltage leads the current by 90°, and ICE means in a capacitive circuit the voltage lags the current by 90°.
I knew you’d be impressed. Now go be the life of some party somewhere.
The Planets: (as I was tought early on…)
My Very Educated Mother Just Served Us Nine Pickles.
You missed the best one!
Sado-masochistic barbecue - SMBBQ:
Staten Island, Manhattan, Brooklyn, Bronx, Queens
I’ve always used the names of the planets as their own mnemonic – no need for mothers making sandwiches or any of that.
And I can sing the names of the 50 states in alphabetical order to the tune of “Fifty Nifty United States” from Let George Do It, the American Revolution-themed musical play that we performed in the second grade. It was my best Stupid Human Trick for a long time, but now that I’m a copyeditor it comes in handy when I run across a list of addresses or organizations by state in a manuscript. 
Mother Very Thoughtfully Made A Jelly Sandwich Under No Protest.
(The “A” is the asteroid belt).
Damn it Scarlett67, I thought I was going to get to be the first one to mention “Fifty Nifty United States”, but on the LAST post before I ring in there you are!
I have another geography mnemonic :George eats old gray rats and paints houses yellow.
“Never separate a para from his parachute” (to spell separate)
“Please Stop Cars Motorbikes and Zebras Invading Tiny Leicester City, Making Sausage Gravy Pink” [:)]
For the reactivity series of metals
FeMAle
Force = Mass * Acceleration
DeSTination
Distance = Speed * Time
Yes, I use SOHCAHTOA still now as well
Remembering how to set a table: fork and left both have four letters, so the fork goes on the left. Spoon, knife, and right all have five letters, so the spoon and knife go on the right.
I can also spit out my company’s tax i.d. # without thinking cause I came up with a code for it. Impresses the hell out of people who ask for it. But I’m not posting that here.
I’m surprised no one tosed this one in here. My high school chem teacher gave us:
“Have No Fear Of Ice CoLd BeeR.”
The capitalized letters are the seven elements (hydrogen, nitrogen, fluorine, oxygen, iodine, chlorine, bromine) which form autodiatomic molecules in nature.
LL