Create a hand-drawn sketch

Because you always start from nothing when modelling a system and drawing a diagram for the model you have in mind, start with a pen and paper sketch. You will have to find a basic layout, a task which is done much faster on a piece of paper or on a whiteboard than with Visio.

Your final sketch on paper might look like the following (keep in mind that we want to achieve the diagram shown in the start of the Tutorial but don't actually posses it).