During the years I spent helping entrepreneurs post "financing wanted" bulletins at my company's website, I formed an opinion about the style of executive summary that angel investors and venture fund managers want to read. Here are the highlights.
Factuality, clarity, and brevity
Busy reviewers have little time for abstract, obtuse or lengthy prose. So take your time to make each statement concrete, comprehensible, and concise. Use plain language and declarative sentences to say everything you want the reviewer to know, in the fewest possible words.
What to say
Give the reviewer a keen sense of your management vision, human and physical resources, market opportunity and resource needs. Indicate how resources you seek would be used to achieve your project's goals and objectives. (Make it clear that your "market opportunity" numbers are "estimates.")
What not to say
You should not, and need not disclose any of your business secrets. Before obtaining bona fides that satisfy you, don't let the cat out of the bag, so to speak. Don't say, for instance, "Roquefort cheese makes our mousetrap better." Better to say, "Tests show that our product's secret ingredient makes it the first choice of French restaurant owners," or serious words to that effect. Also serious: make no promises or offers to sell securities. (You should seek professional advice before entering into any financial negotiations.)
In summary, "KISS""Keep it succinct and short" (not much longer than this article). Let the reader know that your business plan with detailed financials is available for review, pending receipt of the reviewer's bona fides. Make your location and time zone known. And make it convenient for the reviewer to contact you.