In this tutorial we will look at the simplest non-trivial multi-scale approach – so called sequential multi-scale method. The prerequisites for this method to be applicable are (i) scale separation, i.e., existence of at least two distinctly separate length scales, and (ii) full decoupling between these length scales, i.e., physical processes at each of these scales can be considered independently. The method will be illustrated using a simple example problem, and then applied to modelling fluid flows over and through complex surfaces. Different possible approaches in creating such models will be discussed.