User experience design is an important part of software product development, and yet software product line engineering has largely ignored this topic. This paper presents a set of industry best practices for user experience design in software product lines. We conducted multiple-case case study research using two different product lines within the multinational company Siemens AG: in a healthcare software division and in an industrial automation software division. We performed a preliminary exploratory study that will serve as a baseline for future research in the design, implementation, and management of user experience design in the context of software product lines. Practitioners can use our findings and the resulting best practices to improve their user experience design, particularly within healthcare and industrial automation software product lines.