begin with very short notes book, after that extend your knowledge, you must have a good background in chemistry( both general and organic), physics, and biology, be patient, be interest, be funny. You should remember that physiology and biochemistry are the two faces for one coin.
It depends on the person. Every people have different way to learn. My suggestion is "from the big picture to the smallest detail". The best you have a overview understanding before going into the detail parts.