I would say the "definitive" answer is in the technical manual for the dance, such as the "Man's/Woman's Part" within Ballroom Dancers.com (BRC). These are pretty good and generally follow other "official" tech manuals. For example, as far as I can tell, the International Ballroom dances in BRC are exactly the same as found in the official International Society of Teachers of Dance (ISTD)technical manual. A good manual, coupled with a good teacher, is probably the best combination for becoming a good dancer. Otherwise, any information you could want can be found on line by searching Google or YouTube, being aware that there's a lot of really bad information out there. Good luck.