With the rise of Extended Reality (XR) technologies, such as head mounted displays (HMD) for Virtual Reality (VR), Mixed Reality (MR), and Augmented Reality (AR), designers are presented with many unique challenges and opportunities when creating applications. Publications can be found from research and industry that offer insights and ideas surrounding user experience (UX) for XR applications. However, these publications often vary in format and content. Based on a thorough analysis of 68 different resources from research, industry, and 2D design, we present a set of eleven UX guidelines for designing XR applications. Our work serves as a reference to the literature for understanding what others have tried and discovered and provides an integrated set of guidelines. Furthermore, our guidelines offer guidance to a software developer to aid in the design of XR applications for HMD devices.