When I went through Basic Electricity and Electronics, at Great Lakes, I learned about resistors. These little widgets come in many values (as measured in ohms), and they're colour-coded so people can tell them apart - little stripes of different colours (each colour representing a different number) are painted near one end of the resistor, and one who knows the code can read these stripes to know what sort of resistor it is. To learn the code, we were taught the sentence "Bad Boys Rob Our Young Girls Behind Victory Garden Walls;" the initial letters of the words are the initial letters of the colours, and the values are, in order, one through zero.
*From Great Lakes I went out to San Diego for A school (in those days all radiomen, sub or skimmer, attended the same A school). My brother had served 20+ years as an IC, retiring five and a half years before I enlisted, and he was still living in San Diego at that time, so I spent as much time as possible at his house. One day I mentioned the above sentence to him; he laughed, and said that in his day it was "Bad Boys Rape Our Young Girls But Violet Gives Willingly."
Such sayings as these are known as mnemonic devices, things to aid one's memory. There are lots of them around; I think it was in eighth-grade music class that I learned "Every Good Boy Does Fine" and "FACE" - the notes which fall, respectively, on the lines and on the spaces of the treble clef.
Need to know the proper order for various taxonomic groupings? "King Philip Came Over For Good Soup" (kingdom, phylum, class, order, family, genus, species).
How about the order for geological time periods? "Camels Often Sit Down Carefully. Perhaps Their Joints Creak? Proper Early Oiling Might Prevent Premature Rusting" (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Recent - and if you want to split the Carboniferous period into the Mississipian and the Pennsylvanian, substitute "Mighty Precariously" for "Carefully").
Or you can memorise the following little poem:
Sir, I send a rhyme excelling
In sacred truth and rigid spelling.
Numerical sprites elucidate
For me the lexicon's dull weight.As long as you spell it correctly, you can count the letters in each word and come up with 3.14159265358979323846 (sound familiar?).
I love these things, and history has always been my favourite subject, so it was with great joy that I discovered the following:
Willie, Willie, Harry, Stee,
Harry, Dick, John, Harry Three;
One, two, three Neds; Richard Two;
Harry four, five, six - then who?
Edward four, five; Dick the bad,
Harrys twain and Ned the lad;
Mary, Bessie, James the vain;
Charlie, Charlie, James again.
William and Mary, Anna gloria;
Four Georges, William and Victoria.
Edward the Seventh next, and then
George the Fifth in nineteen ten.
Edward the Eighth soon abdicated,
And so a George was reinstated.
Bessie again, to end the list,
And that's the lot - not one's been missed.** And in case you haven't figured it out by now, that's a list - in order, of course - of the reigning kings and queens of England/Great Britain/the United Kingdom, from William I to Elizabeth II.
* See here if you really want to know the whole thing.
** Well, actually both Maud and Jane have been missed, but....