This guide describes how states can plan the implementation of their section 1115 Medicaid demonstrations to enable rigorous evaluations. Though the strategies discussed here can apply to a broad range of demonstrations, we focus on evaluating eligibility and coverage (E&C) policies. Recent policies of this type include community engagement requirements, premiums or monthly contributions to beneficiary health accounts, non-eligibility periods as a consequence for noncompliance with program requirements, healthy behavior incentives, and retroactive eligibility waivers.1 E&C demonstrations often apply more than one of these policies to the target population. They also influence beneficiaries’ likelihood of separating from Medicaid. This means E&C evaluations must examine beneficiaries’ outcomes after they disenroll or are removed from Medicaid rolls, which in turn creates a need for longitudinal beneficiary surveys. For these reasons, E&C demonstrations are particularly relevant to a discussion of how implementation can strengthen evaluation design.