The method is how one intends to answer the research question based on evidence from outside oneself. Scientists describe their method so that others can follow in their footsteps. For formal sciences like mathematics, the method based on formal logic is so well known it is not usually described. For the natural sciences, the method varies considerably and so must be described. Aspects of the method include:
See a textbook like Essentials of Behavioral Research: Methods and Data Analysis, 2007, by Robert Rosenthal and Ralph Rosnow for full coverage.