This guide aims to support state education agencies and early education partners develop coherent, research-based policy by guiding thinking, discussion, data collection, and gap analyses of current practices and policies that can lead to more intentional decision making relative to young Dual Language Learners (DLL) and English Learners (EL). This guide prioritizes 6 of 13 big ideas presented in the National Academies of Sciences, Engineering, and Medicine (NASEM) report, "Promoting the Educational Success of Children and Youth Learning English: Promising Futures," which provides focused, actionable steps that State Education Agencies (SEAs) can take. The State of Preschool 2017 special report on state policies for young DLLs from the National Institute for Early Education Research (NIEER) found that of nine policy requirements for effectively serving preschool DLLs, 26 state-funded programs out of a total of 60 lack any policy to support the DLLs enrolled in their programs. Also, this guide prioritizes the significance of data collection at the state level, as several recent research reports note the extent to which this data on the implementation of policy specific to this population is missing. For example, The State of Preschool 2017 reports that of 60 state-funded preschool programs in the U.S., only 26 are able to report the home language of children being served in their programs. The lack of information about home language is just one example of missing data; these data gaps among state-funded preschool programs are perilous as they create missed opportunities to provide access and quality to DLLs in significant ways. While the NIEER state preschool yearbook reports only state policy, there may be local policies or practices that do help inform opportunities for DLLs and create coherence across districts and grades. Increased awareness among SEAs of these policies and practices from PreK to grade 3 programs could facilitate development of relevant statewide policy. Indeed, this can only be done through systematic data collection and communications between and among SEAs and LEAs. [For the NASEM report "Promoting the Educational Success of Children and Youth Learning English: Promising Futures. Consensus Study Report," see ED582056.]