I find that, if it's a concept completely foreign to me and it took me 30 minutes or more to figure it out, I'll write a blog post on it. (Did so, recently, with the Swedish Personnummer and Luhn Algorithms.)

This mightn't help anyone else but me but the fact that I took the time to try to explain it to someone else means I've had to try to solidify my own understanding of it before attempting to explain it to someone else - if that makes sense? Perhaps, even the fact of writing it down helps me to remember it that much more because I have to present it as consumable material to someone who may not just "get it" from the onset.

Heh. I almost always type 'grep foo bar' and let the error tell me the right order because I never recall if it is needle haystack or haystack needle. I do this a lot.