My crib notes/highlights from this Early to Rise article I read years ago: http://www.earlytorise.com/how-to-sell-anything-including-your-ideas-and-yourself/
For selling, writing, speaking . . communicating.
"The message is about the reader and his interests, needs, and desires, not you and your wants."
"It should contain some significant promise of benefits (again to the reader), implicit or stated.
"The benefits should be concrete -- easy for your reader to imagine."
"Any claims you make should be supported by facts."
"Difficult concepts should be included only if you can clearly illustrate them with examples and analogies."
"Simple is better. One overriding idea presented repeatedly in different ways and with building evidence is much stronger than a string of related but distinct ideas."