Planning a lesson can be similar to planning a road trip--a metaphor the authors use to describe how they applied research and theory to their lesson planning process. A map and mode of transportation, the Common Core State Standards for Mathematics (CCSSM) and textbooks as resources, can lead to desired destinations, such as students engaging in cognitively demanding tasks and making connections between their learning and the world around them. In the authors work with teachers collaboratively planning with the Common Core State Standards for Mathematics (CCSSI 2010), they have found that this metaphor is helpful in keeping track of the progressive phases of lesson planning and maintaining focus on complex decisions without losing a sense of overall goals. In this article, the authors describe key aspects of lesson planning in four phases and include an example of a lesson on linear functions taught by coauthor Estes in a ninth-grade first-year algebra class. Although lesson planning involves countless decisions beyond what could be captured in their example, the process they describe highlights important phases in planning and can be used for any mathematics lesson.