Some unseen force in the textbook-writing industry decrees that every writing text must include some variation on this statement: You have to find the method that works for you. I immediately want to dial up Captain Obvious to report a cop-out, but then I recall that I gave that same advice to one of my own students just last week. It's true--you do have to find the method that works for you--but the problem arises in how we understand that word works.
Context matters. The method that enables E.L. James to write Fifty Shades of Gray will not necessarily serve the student attempting to write a research paper for a first-year composition class, and telling certain lazy students do what works for you sounds like permission to do nothing--or to plagiarize. (Which, lest we forget, helps students develop the time management skills that they need to succeed in the world of work.)
First-year writers in composition class need to find the method that works to demonstrate mastery of certain conventions of academic writing. A student comfortable with sub-par performance might smile and say "It works for me!" But it may not work to produce the desired grade.
Upper-level classes are different. With first-year writers, I tend to issue directives: you must put the parentheses here; you must properly integrate and punctuate quotations from sources; your thesis statement should follow one of these helpful models. Advanced writers get gentle nudges: try this clause at the beginning of the sentence and see how it changes the emphasis; consider more vivid verbs here and see how they impact meaning and rhythm; have you thought about switching these two points around? Give it a try and see what works. It's like the difference between giving a preschooler a coloring book (Color inside the lines!) and giving an older child a blank canvas and a bunch of paint.
Do what works for you works best for writers who know enough about writing to know what works best. In that way, it's like much writing advice: most useful for those who don't need it.