The cross diagram is a way to illustrate and plan the solutions for all kinds of constant-acceleration kinematics problems--including projectile motion, multistage, and multiple-object problems. The cross diagram arranges the kinematic variables in a logical way, making the kinematic relationships between them easy to identify. Combined with a method to visually mark known information and equations, it provides a framework to plan out which equations will be used in the solution of a problem. This paper introduces the cross diagram through its use in a series of example problems.