Every successful IT project starts from the company's needs. The best way to identify this is to describe the business processes. Each process consists of several steps that provide a certain input and are performed by something or someone. These steps eventually result in output on which a decision can be made.
Often, a "Function flow diagram" is used to visualize such processes.
By describing the processes, one also learns to understand and discover the strengths and weaknesses. In short; an indispensable tool for taking on any IT project.