The purpose of the conceptual model is twofold:

• To help communication, and  ensure agreement, between the various stakeholders about what the issue actually is – and within that what is important and what is not;
• To provide a clear and concise description of the system of interest (i.e. all the main components and their relationships), as a basis for assessment.

Building conceptual models is not easy, and several, repeated attempts are likely to be necessary.  One of the most  difficult challenges is to define clear boundaries to the issue, in ways that do not unfairly limit or bias the assessment. (see link to Setting boundaries).  

Initially, also, the models often become progressively more complex, as new elements of the issue (and in some cases new stakeholders, with different interests) emerge.  Later, however, it is helpful to simplify the models, in order to remove elements that are not important or unclear, and focus on those aspects that are considered most important (see the link to the examples to the left, and under See also, below).

Conceptual modelling can be done largely intuitively – for example, by simply drawing up a diagram through a process of collective debate.  More formal methods are available, however, which help to rationalise the process; probably the two most useful and flexible are mind-maps and systems diagrams. 

Which is most appropriate is likely to depend on the experience and skills of those involved, as well as the complexity of the issue.  No matter which technique is used, it is also helpful to structure the model in terms of the causal chain (or some other, predefined framework) in order to make sure that it is logical, consistent and complete.