Practitioners in user-centric industries have increasingly recognized the applicability of personas. However, the methods used to create personas in different domains remain inconsistent and unsystematic. We analyzed 51 studies focused on designing personas for professional purposes and find the practice most prevalent in the user experience (UX) design, healthcare, market research, and social media strategy domains. Within these domains, UX design personas are characterized by their focus on user activity and goals, market research personas on customers' lifestyles, health personas on medical patients' physical symptoms, and social media strategy personas on interactions within online communities. We identify and compare the elements in the personas. Based on this, we provide guidelines for professionals interested in developing personas for recruiting users, understanding barriers to positive user experience, and building online communities, including how to represent persona details related to lifestyle, contexts of product usage, and scaling of online data.