Eno and Schmidt's deck of cards — 'Honour thy error as a hidden intention', 'Use an old idea', 'Discard an axiom', 'What would your closest friend do?' — was made for studio sessions where the obvious next move had been worn out. The trick is the cards are deliberately oblique: not domain-specific advice, but provocations from far enough sideways that the mind has to twist to apply them. The twist is where the new direction comes from.
The principle: When you're inside a problem, your next thought is constrained by the previous thought. A random external instruction breaks that chain. The advice doesn't need to be 'right' — it needs to be other.