What are the two principles established for the Best American Fantasy series according to Matthew Cheney in the preface?

The two principles are that each book will have different guest editors after the second volume and that editors are encouraged to search broadly for stories that fit their conception of 'best,' 'American,' and 'fantasy.'

Matthew Cheney establishes two principles for the Best American Fantasy series. First, after the second volume, each book in the series will feature different guest editors. This approach aims to bring diverse perspectives and interpretations to the selection process. Second, editors are encouraged to search as broadly as possible for stories that align with their own understanding of what constitutes 'best,' 'American,' and 'fantasy.' This principle is rooted in the belief that great writing can emerge from unexpected places and forms, challenging traditional labels and expectations.