Ubiquitous computing systems present a unique set of challenges to designers, such as novel interaction techniques, the ability to detect and respond to their context of use, and unconventional user interfaces. To understand how designers currently address these challenges, we conducted more than a dozen in-depth interviews with designers of a variety of ubicomp systems. Our analysis of these interview and the artifacts used in the design of these systems revealed a number of difficulties in the design of ubicomp systems. Furthermore, it illuminated a pattern of design practices that differs from the design of conventional interactive systems. This ongoing research seeks to develop patterns and practices to support the design of ubiquitous computing systems.