I’ve been playing around with electronic projects for decades, but still it happens (too often) that I just can’t remember if the flat spot of the LED is the anode or cathode (it’s the cathode. I looked it up. 10 seconds ago). And I have to google the pinout of a 2N3904 every time I have to use it.
So finally I made a cheat sheet. Simple stuff, but I use it every day.