All writing is persuasive writing—first you must persuade the reader to keep reading, if for no other reason than to justify your labor. You must persuade those who paid for your work that their money has not been wasted, and you must persuade your inevitable critics that you have sufficient credibility to make your argument. A fiction writer might have five pages to make their case. A technical writer is lucky to have five paragraphs to cover the same territory; more likely, five sentences. Nobody is reading your work for fun, so you have to set your scene quickly, directly, and elegantly.
Who, what, when, where, why, and how? Who is involved, what is the situation, when did it start, where can it be found, why do we care, and how bad is it? There are potentially carcinogenic fracking chemicals in drinking water in Pennsylvania. The city council needs to know more about backyard chicken raising before changing an ordinance. Congratulations, you have just purchased our software! In the case of Smith vs. Jones, the defendant requests a dismissal on the grounds that the plaintiff has not suffered damages. When in the course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, … a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.
As far as the mechanics goes, just say it straight out, using clear, direct language that commands the reader’s assent. Don’t imply, don’t infer, don’t force the reader to come to their own conclusions. Imagine that they are busy people who want to be told what to think, preferably somewhere on the first page.
Note: this is for non-fiction writing. In fiction, half the fun is in implying things. However, setting up a red herring in a policy document? Ninety percent of your audience will come to the wrong conclusion.