Experience level, not training. Exposure to a variety of different functional areas: recruiting, compensation, benefits, employee relations, organizational development, training. These are key areas where demonstrated ability/knowledge is critical. Certifications such as PHR or SPHR are indicative of HR knowledge/expertise. For Director level, SPHR probably a better indicator of knowledge as there is more emphasis on strategy in the SPHR exam.
Non traditional career paths that I have seen lead to HR management->Operations management and supervision. Probably most significant entry point into the HR function is Staffing/Recruiting.