These three questions are addressed in this section. In Section 3.1 we discuss the basic choice between either using an experimental approach related to the electrochemical analysis of Faradaic systems (often using three different electrodes, of which only one is the porous electrode to be tested), or to follow an approach focusing on desalination performance, using a two-electrode cell with both electrodes consisting of porous carbon. We continue in Section 3.2 with listing various of the possible CDI designs that can be chosen based on the “two-porous-electrode” cell design, and discuss in Section 3.3 which different feedwater compositions can be used in CDI-testing. Section 3.4 discusses two CDI experimental layouts used in literature. The detailed analysis of the CDI cycle in terms of salt adsorption and charge is presented in Section 3.5. In Section 3.6 we introduce the important option of adding ion-exchange membranes to the CDI system, and in Section 3.7 the common method of constant voltage operation is explained and a comparison is made between desorption at zero voltage and at reversed voltage. Finally, in Section 3.8 the distinction is explained between the classical constant-voltage mode of operation and the novel mode of constant-current operation.