Gamified systems combine information system functionality with gamification elements to support motivation and engagement. However, existing gamified system development approaches lack a unified method to identify usability recommendations for both the system as a whole and individual gamification elements. This paper proposes MIURGS, a method for identifying usability recommendations for gamified systems according to user and system characteristics, including age group, application domain, gamification goals, usability goals, and principles. The method is implemented in a dedicated tool and supported by a knowledge base containing usability recommendations and gamification element suitability recommendations. MIURGS was evaluated through two studies: a student experimental evaluation with 45 participants and an expert evaluation with 12 respondents. Results of the student experimental evaluation indicate that for general recommendations, identification, gamification element selection, and ease of identification, tool-supported process results were better evaluated than unaided identification. The expert evaluation further indicated that the method is perceived as useful and relevant, with 11 of the 12 respondents agreeing that it would reduce the effort required to identify usability recommendations.