This book is intended to serve as a handbook that explains how to craft persuasive policy papers. This book may be found in the Cowles (undergraduate) library.
This Stanford Law guide to writing about policy has a couple different ways to analyze potential policy solutions. You may also want to look at the Stanford guide to writing policy white papers.
This guide, from the University of Iowa, is intended to provide information to members of the Injury Prevention Research Center, but it also lays out general tips for crafting a persuasive brief.