- In a classical prisoner's dilemma (i.e. a one-time interaction), always defect.
- In an iterated prisoner's dilemma (i.e. repeated interactions by the same partners), use Tit-For-Tat (respond in kind).
- Be nice, i.e. do not defect on the first move. After that, use Tit-For-Tat. The more interactions there will be, the more important it is to be nice.
- Teaching students: (Iterated) - be nice but firm, sticks are needed as well as carrots.
- Open notebook science: It's not clear to me whether this is iterated or not, which makes a big difference.
- Online identities: (Iterated) - be nice but stand your ground on principles.