Here's how I finally memorized it: ln has a 1-file-argument invocation, so ln -s ../../a_fine_file will create a symbolic link to that file under the current directory and under the "a_fine_file" file name. The single argument case has to have the file you want to link to as input. That generalizes nicely as the 2-file-argument invocation maintaining the logic.
A guy in the office always remembers it as remembering that wedding saying - something old, something new, something borrowed, something blue. Whenever he did a symlink he would always say out loud something old, something new, ... That has stuck with me as well for all these years so I've never needed to figure out which was which, I always just knew it.
> In the early eighties you would have found the Space Invaders cabinet in an arcade right next to the pinball machines. So a "tilt" switch, like you would find in a pinball machine, would not have seemed as strange as it does today. If you shake, slap, or otherwise physically abuse an SI cabinet you will get a TILT message and your game will end.