Which parts of the organization must be modeled? What is the correct sequence? To what level of detail should the modeler go? There has to be a trade-off between too much detail and too little. These are the issues that a methodology is designed to solve. A methodology is a process. Therefore it is repeatable, consistent, and can be learned.
The logical methodology is to start with the goals of the organization, then work down to identify the products and services that support those goals, and finally examine the processes and elements that deliver those products and services. However, we do not recommend this approach unless there is very strong and unified support for modeling at a senior management level. The reason is that the achievement of goals is political and different factions will compete to push their own agendas.
In some organizations the order is reversed, with initiatives that model aspects of specific processes, where there is buy-in for a modeling approach...