This chapter presents a practical guide to developing new Science, Technology, Engineering and Mathematics (STEM) classroom assessments, and/or modifying current STEM classroom assessments, to be better aligned with integrated STEM curriculum and instruction focusing on learning of complex real-world concepts and practices in order to represent student learning in a valid manner. It also provides guidelines and examples on how to use STEM classroom assessment results. The chapter focuses on Bloom's Cognitive Taxonomy since it is widely used in science education. It reviews the basic decision to be made on deployment of the item type and the fundamental rules associated with writing each type of item. The goal in assessment is to maximize information and minimize error. Using the practical strategies provided in the chapter to develop new STEM assessments or revise current STEM assessments will lead to more effective assessment practices that produce results more representative of actual student ability while minimizing error.