Schools are required to provide English Language Learners (ELLs) with specialized instruction as determined by federal and state laws and regulations. However, service delivery options vary from state to state and from school to school based on policies, mandates, demographics, and a range of other variables. Collaborative practices and co-teaching--also referred to as integrated service or inclusive ESL in some states--are becoming increasingly widespread across the country. This guide is presented as a quick reference for K-12 ESL teachers and their general education colleagues, as well as their coaches or administrators. It is designed to support all educators of ELLs as they engage in a complete collaborative instructional cycle consisting of co-planning, co-teaching, co-assessing, and reflecting on their practice.