Guidelines for Preparing Functional Requirements Document

Extract the independent actions/tasks/activities from the product overview document. Each one of these may correspond to an individual functional requirement. Sometimes, a few of these tasks might be combined together into one functional requirement.
Separate the data to be manipulated from the tasks/activities to be performed. The data serve as input and/or output for the functional requirements.
Analyze the list of tasks/activities and the data for complete coverage of information with respect to the product overview document.
Follow the standard template in creating the functional requirements document.
Try to group the functional requirements into various subsections; these subsections depend on the application domain and the requirements document.
Ensure that no implementation-oriented details such as types for parameters, format for data, representational details and algorithmic details are included in the requirements document.
Every functional requirement is written in such a way that it is more or less independent of other requirements. For example, you may have to repeat some input parameters again and again in every functional requirement in a section.
You should not assume any context associated with a functional requirement. For example, you cannot assume that functional requirement FN.1 will be called from functional requirement FN.23 and hence the output parameter of FN.1 will be used in FN.23. As stated earlier, each functional requirement is more or less independent on its own. The design process will tie them together.
Every data item mentioned in "Action", "Exception", and "Remarks" sections must be declared either in "Input parameters" or in "Output parameters" but not both.