We have lots of markers in our house but not as many papers lying around, so I often turn to my hand when I need to write something down. The hand actually makes a perfect reminder, I see it all the time and I can´t loose it (like I always do with small notes).
But when it ´s super duper important (a matter of life and death-type of thing) I also X my foot. It´s the first thing I see in the morning, so it can´t go wrong.
When John Waters (book-Role Models) recommends a movie or a “single-named” bombshell I write it on my hand.