I use a few "cute" mnemonics when there are some things I just can't remember and I'm curious as to what ones other people use.
grep, I usually can't remember if the pattern comes first or the file, so I think of my mother-in-law who cross stitches and the "pattern files" she uses:
grep <pattern> <file>
find, similarly, I think of "location flags" planted in the world:
find <location> <flags>
Of course, tldr is the real hero here.
For markdown links, I usually can't remember if it's
(text)[link], but b comes before p, so brackets come before parenthesis.
P.S. The worst "anti-mnemonic" is how in Vim
gg goes to the beginning of the file, but in Starcraft, you always say "gg" at the END of the game :P