In clinical or educational practice, it is often necessary to use an individually tailored, sequential approach to intervention in order to improve outcomes. Adaptive interventions (also known as dynamic treatment regimens) can be used to guide such sequential intervention decision-making. Adaptive interventions are multicomponent, multistage intervention packages. The multiphase optimization strategy (MOST) is a comprehensive research framework for development, optimization, and evaluation of multicomponent intervention packages, such as adaptive interventions. When working within the optimization phase of MOST, behavioral, biobehavioral, and educational intervention scientists often have important scientific questions about how best to optimize an adaptive intervention. This chapter discusses various types of experimental designs that can be used to optimize an adaptive intervention. In some of these, participants are randomized once over the course of the trial (i.e., singly randomized trials, or SRTs), and in others, participants are randomized at multiple stages (i.e., sequential, multiple assignment, randomized trials, or SMARTs). The choice between SRT and SMART ultimately is driven by the scientific questions that the intervention scientist seeks to answer. Motivated by the development of an adaptive intervention to improve social skills and academic engagement among children with autism, we illustrate these ideas by presenting four example of experimental designs: two examples of a SRT and two examples of a SMART. We present the rationale for each experimental design and the questions each is designed to answer. In doing so, this chapter provides an expanded set of tools that investigators aiming to develop an adaptive intervention can draw from within the MOST optimization phase toolbox.