How can a Muslim man/woman know the means of acting upon the the Book of Allah and the Sunnah of His Prophet Muhammad, peace be upon him, and find rulings and commands from the Qur'an and Sunnah?

A Muslim can access Allah Almighty's rulings, commands, and prohibitions through two ways: first, reliable books, such as books of verses and hadiths of rulings; and second, trustworthy scholars. If the seeker combines both methods, it would be more complete and perfect, starting with what is most important, then what is important, and with concise summaries of knowledge. It is not possible to act upon what Allah has revealed before knowing it. Therefore, a Muslim must be keen on acquiring knowledge, then acting upon what he has learned. The Companions used to learn the Qur'an, knowledge, and practice all together.