Business Model Generation looks like a great way of doing this. It's available in many public libraries and on all the usual websites at a reasonable price.
BMD describes a 9-piece way of modelling business models. (Yes, awkward sentence.) Then it goes on to show you how the model can be used to explore Google, the FREE business model and some other 'patterns' that have succeeded. By the end of the book you will have learned how to deal with the various phases involved in producing a business model including imagining, critiquing, evaluating and so on.
Worth a look.