Donella Meadows walks a class through the model conceptualization process in Creating Models from Scratch:
One interesting thing here is that she starts with a causal loop diagram. This is a case where there are some clear physical quantities of interest (people and mosquitoes), so I would probably have started with stocks and flows. (Or, I like to think I would.) But you never know how things are going to go – I can think of other situations where CLDs worked out better. The key is to stay flexible and switch methods as needed, and as the audience requires (see around 30:00 for the stock-flow implementation).