The Business Model Canvas is an excellent tool for defining and challenging your business model. This (slightly modified interpretation) takes you through a structured process of looking into:
1. Customers: Who are our key customer segments that we create value for?
1a. Relationships: What type of relationship do they expect to have with us?
1b. Channels: Which channels do they want to use to interact with us?
2. Value Propositions: What value do we deliver to our customers?
2a. Key Activities: What are the activities that deliver real value to the customer?
2b. Key Resources: What key resources are required to perform those activities?
2c. Key Partners: If we do not need to have all of the resources, who do we need to partner with?
3. Revenue is earned from: How do we charge for the products/services and from whom?
3a. Key Costs: After we have incurred all of the costs, will the business model be profitable?
4. Annual Calendar: What happens month to month?
4a. Annual Budget: What is expected to happen financially?
4b. Targets: How do we know the business model has been successful in year 1, 2, and 3?