Each person uses his own method for taking notes. Whatever the method, it is important that it be efficient and easy to use.
Some students find it helpful to use 3" x 5" or 5" x 8" index cards for taking notes of their research. If you use this system, you can devote each card to one piece of information about your topic. On top of the card put a heading to identify the subject matter (ex. "Food Requirements for a Family of Five on Welfare"). This system may help you arrange your cards and your ideas in an orderly way. After doing all the research, you can spread the cards out and restack them according to your subject headings. This will help you organize an outline for your essay. You may find, after doing all your research and preparing an outline, that some of your notes are irrelevant or excessive. Just exclude them; don't force them into your paper.
On the same cards, make note of the page numbers of the book as well as full bibliographical information: author, full title, publisher, and place and last date of publication. For a periodical article, put down the author, title of the article, volume and issue number, date, and page numbers.