I'd add to the "Understand" part: should include samples (screenshots, logs, output files, etc), where appropriate.<p>This helps with understanding for the review, and also if it's referenced again in the future (eg, someone is coming back to fix a bug that's later found to be introduced by the change). It takes only a minute or two extra to do this, while saving the reviewer a lot of time (checking out and running) and/or mental gymnastics (reasoning about what CSS/html changes will actually look like).<p>Obvious example of where this is useful is for a UI change (with before+after and/or annotated screenshots), but I've also found this useful for timing bugs (eg logs), and data-driven code (eg where output depends heavily on data).