[gregmac]

I'd add to the "Understand" part: should include samples (screenshots, logs, output files, etc), where appropriate.

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).

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).