This is a far bigger problem than some here might think. I write emails now on the assumption that the recipient might read the first two sentences, skim the first two paragraphs, and ignore the rest.
Whenever I write a report I always put the summary first because that is all that anyone who trusts me needs to read. The rest is supporting information and extended arguments in favour of the proposition that I make in the summary together with some notes about why alternatives are no good.
Of course, I never went to business school, I'm an engineer who started as a physicist.