If you were writing maxims for being:
a) A good playtester
b) A good designer during a playtest
what would you write? These can be as specific to your needs, or as broad/general as that you think it should apply to anything.
Examples of maxims:
* Playtester: Don't break the game.
* Designer: Don't get angry at people's feedback.
* Playtester: Describe how you felt, not how you would fix it.