Actually, it’s quite simple, as Donna Spencer points out:
Just make it up.
Wait? Is it that simple? But in order to make it up you just ned one thing: information.
You need to understand what you are trying to achieve, what users of the service need and know, and you need to know the content well. If you donâ€™t have these things, it will be hard. But if you do have them, pulling them together into a first draft is surprisingly easy.