Who, What, Where, Why When and How.
Used in journalism but just as easy to remember for this purpose. Covers everything, some information may be edited down.
Who you are and your audience is, what you intend to do, where you intend to do it, why you intend to do it (daylight, fuel, weather, panpan or other emergency? may be left out for routine communication), when you intend to do it (ETA, departure, action) and how you intend to do it (runway).