Over the last two years, the author has talked with thousands of educators about the Common Core State Standards, and she has realized that one of the biggest risks they currently face is full-speed implementation without an understanding of the changes that the standards require. When a new reform initiative comes around, the instinct of teachers and education leaders is often to buy new tools to support the work. But in a time when the market is offering an enormous range of materials, educators need a secure understanding of the standards so that they can choose their resources wisely. As they put the standards into practice, it is important to focus on a few shifts that have the most significant effect on students. These shifts should guide all aspects of implementing the standards--including professional development, assessment design, and curriculum. When educators attend to three core shifts in English language arts and literacy as well as in mathematics, the expectations for teaching and learning will be clear, consistent, and tightly aligned to the goals of the standards.