The performance of a Shack-Hartmann wavefront sensor is largely determined by the design of the lenslet array. In its simplest form, there are two available design parameters: the number of lenslets across the diameter of the wavefront, and the focal length. Spatial resolution, sensitivity, accuracy, and dynamic range are all affected by one or both of these parameters. For example, by virtue of increased spot motion under a fixed wavefront slope, longer focal lengths provide greater slope sensitivity. Simultaneously, longer focal lengths reduce the dynamic range, since spots may overlap for smaller wavefront curvatures. This paper presents a graphical approach to lenslet array design where various considerations constrain the possible solutions of the design problem.