or a technique I have used a few times
a mnemonic acronym or a mnemonic phrase based on the first letters.
For example, with:
“A Red Fox Found A Key Under A Tree And Ran To The Mountain.”
You take the first letter of each word:
A R F F A K U A T A R T T M
And you can transform it into:
ARFFAKUATARTTM7!
Another technique is to keep some words intact and use initials for the others:
RedFox!FKUATTM7
The advantage is that you remember the original phrase, not the string of characters directly.