Kipling's Advice for Project Managers

I keep six honest serving men
(They taught me all I knew);
Their names are What, and Why and When;
and How and Where and Who.

– Rudyard Kipling (1865-1936).

Any plan must

1. Set out the objective - the "What". 
2. Explain the reason - the "Why".  
3. Specify the steps that are to be executed - the "How".
4. Specify time sequence for execution - the "When".
5. Specify the place, or the objects, where, or on which, the steps are to be completed - the "Where".
6. Specify the persons responsible for the execution of the steps- the "Who".

Come to think of it, source code documentation too, with the possible exception of #6, should have the same information.