The move from theory to empirics requires figuring out how to collect evidence that could support or disconfirm hypotheses derived from your theory. Empirically studying the network in your theory requires two steps: determining which nodes to include in your data and operationalizing the link type. This chapter helps a reader select the boundary that contains the nodes of interest, pointing out some subtle downsides to random sampling in network studies. It also helps readers determine whether they want to measure full networks or ego ones and offers pointers on operationalizing link types.