From pp 92-93:
Choose one precept of your religion:
• Your religion preaches the sanctity of suffering, add Petition: Suffering
• Your religion is cultish and insular, add Petition: Gaining Secrets
• Your religion has important sacrificial rites, add Petition: Offering
• Your religion believes in trial by combat, add Petition: Personal Victory
Divine Guidance
When you petition your deity according to the precept of your religion, you are granted some useful knowledge or boon related to your deity’s domain. The GM will tell you what.
I think that this move can put distinctive demands on the GM - especially deciding whether to go with a boon or a soft GM move. But I think it's reasonably clear how it works:
When a player describes their character doing something that triggers a move, that move happens and its rules apply (p 18). So if the cleric does something that falls under the petition that pertains to their precept (ie
suffers,
gains a secret,
makes an offering or
achieves a personal victory) then the move has been made and the GM has to do his/her bit..
For instance, if the cleric whose religion believes in trial by combat achieves a
personal victory, then s/he has made the Divine Guidance move and hence the GM tells her what boon or knowledge s/he receives. Suppose her deity's domain is Civilisation, then maybe the cleric gains insight into the customs of the defeated enemy (say +1 forward to next Parley attempt against a similar sort of being). Or maybe the PC gains a vision of the larger threat of which the defeated foe is a harbinger (Reveal an Unwelcome Truth).