I've never tried the PAO system, due to the startup costs of pre-memorizing 100 person-action-objects.
But a simpler alternative which requires less work up front is the Major System (sometimes called the Phonetic system) [0].
The way it works it by assigning each digit a sound-value (or family of sounds). To remember a number, you then convert the digits to the letter-sounds, and fill in vowels that don't have a digit value to create words.
E.g. to remember Boltzmann's constant, I do this:
1.38 x 10^-23
1 has the letter value "t" or "d". So I use the word "tea" ("e" and "a" have no digit value), to remember the digit 1.
The 38 is converted to "m" and "v", which becomes "movie".
23 becomes "n" and "m", or "nemo", the fish from Finding Nemo.
Putting it all together it becomes: Ludvig [1] walking on bolts (= Ludwig Boltzmann), and in his right hand he's holding a old VHS movie on top of which balances a cup of hot tea. In his left hand he holds a frozen (to indicate the negative sign in the exponent) Nemo.
To make it memorable you can make this scene as vivid as possible: Ludvig is a cautious character who sniffles a lot; walking on bolts would hurt and make it difficult to balance the cup of tea on top of the movie; the frozen fish would be cold and slippery in the hand; the tea would smell nice; etc.
But a simpler alternative which requires less work up front is the Major System (sometimes called the Phonetic system) [0].
The way it works it by assigning each digit a sound-value (or family of sounds). To remember a number, you then convert the digits to the letter-sounds, and fill in vowels that don't have a digit value to create words.
E.g. to remember Boltzmann's constant, I do this:
1.38 x 10^-23
1 has the letter value "t" or "d". So I use the word "tea" ("e" and "a" have no digit value), to remember the digit 1.
The 38 is converted to "m" and "v", which becomes "movie".
23 becomes "n" and "m", or "nemo", the fish from Finding Nemo.
Putting it all together it becomes: Ludvig [1] walking on bolts (= Ludwig Boltzmann), and in his right hand he's holding a old VHS movie on top of which balances a cup of hot tea. In his left hand he holds a frozen (to indicate the negative sign in the exponent) Nemo.
To make it memorable you can make this scene as vivid as possible: Ludvig is a cautious character who sniffles a lot; walking on bolts would hurt and make it difficult to balance the cup of tea on top of the movie; the frozen fish would be cold and slippery in the hand; the tea would smell nice; etc.
[0] https://en.wikipedia.org/wiki/Mnemonic_major_system [1] https://pbs.twimg.com/profile_images/525793520662380544/w9GJ... A character in an iconic Norwegian film.