This working paper describes our collaborative thinking about the promising approaches for implementing policies at sufficient depth and scale to make a difference for young children. It begins with a brief review of research on effective early childhood teaching practices. We contend that professional development and accountability structures need to have a laser focus on supporting teachers to enact these practices. We then describe several "implementation factors" that determine whether policies actually support early childhood teachers' consistent use of research-based practices on a day-to-day basis. The paper then delves into four particular "problems of practice" that state leaders are currently wrestling with as they strive to implement particular policies and practices. The paper is meant to provide a springboard for our ongoing work to support states as we collectively move toward solutions to the challenge of providing all young children with opportunities to thrive in early childhood programs across the country. (author abstract)