This document introduces PLATTER, a planning tool for digital repositories. It discusses what a digital repository is, the importance of trust for repositories, and the challenge of establishing standards for trust given the lack of widely accepted ones. PLATTER aims to help repositories plan for trust by providing general principles, examples, and a process for setting repository-specific goals. It uses a framework of 10 core principles and 4 axes of characterization to guide strategic planning. The planning cycle in PLATTER is based on SMART objectives to help repositories systematically work towards established goals.