Class diagram - Model-driven
Create a class diagram of your application. You may only write the classes' names first, maybe with some attributes/methods, and come back after creating some sequences diagrams.
The relations between classes are the representation of the references. If
A got a reference which is an instance of
B then we have
A -> B (and you may write the instance's/variable's name).
Side note: I'm enjoying using different colors for the different kinds of classes like the classes of the VIEW, the MODEL, and the CONTROLLER (and maybe one too for the events if I'm in the mood).