In this tutorial I will introduce the theoretical and simulation methods most frequently employed to investigate ferroelectrics and related materials (polar dielectrics, antiferroelectrics, multiferroics). I will start from the general electronic-structure methods that permit predictive calculations at the atomic scale, and introduce successive simplifications to eventually reach continuum field schemes that give us access to the mesoscale. I will illustrate the specificity and usefulness of the different approaches by presenting, for each of them, one or two classic examples of application. In passing, this will allow me to emphasize the key role that simulation has played in our field, and to touch upon interesting physical properties of these materials. Jorge Íñiguez’s work on ferroelectrics and related materials is mainly funded by the Luxembourg National Research Fund, currently through projects FNR/C18/MS/12705883/REFOX/Gonzalez, INTER/RCUK/18/12601980 and INTER/NWO/20/15079143.