One other thing I'd like to add is greppable comments! In the same vein as TODO and FIXME, I use hashtags in comments to drop hints to future me reading the code. #learning is a universal one:

// #learning: transparent color using color.new(color.white, 100). This is GREAT for hiding plot() lines during inapplicable periods (such as when no trade is on)

But project-specific hashtags are quite useful, too.

// #60within600: bunch API calls to not hit the 60 calls within 10 minutes limit

// This memoizes fn call results to prevent #60within600

The hashtagging was inspired long ago by del.icio.us, if you remember that. https://en.wikipedia.org/wiki/Delicious_(website)