Doing comparison well comes with many rewards for migration scholars: it challenges taken for granted assumptions regarding immigrant populations, context, and time; it reveals new ways of understanding the social world; and it provides an analytical way to test and advance theory. Comparative research also comes, however, with pitfalls. Poor choices or too many comparisons can make data collection and analysis difficult, time-intensive, costly, and possibly overwhelming. To advance productive comparative research design, this chapter covers why (and whether) migration scholars should use comparative methodologies, what to compare, and how to compare. The question of “what” to compare is about choosing a general conceptual class of “cases.” “How” to compare is about choosing specific empirical cases that drive the comparative logics of analysis. The chapter draws on various immigration-related studies to illustrate these conceptual and methodological choices. Comparison is often based on juxtaposing groups, places and time, but can also compare organizations, institutions and other conceptual units. The selection of specific cases leads to distinct logics of analysis, including typologies, “most-similar,” and “most-different” research designs. Researchers must be thoughtful in ensuring that comparison has a purpose.