You make a card, called a source card, which tells the facts about the source you are using:
Write down the name of the person (author) who wrote the information.
If there is no author given, start with the title of the article or book.
For a book, you will need to write down the author, title, city of publication, publisher, and date of publication. (Add the call number if you are using a library book.)
If you are using an article, you will need to write down the author, the title, and the name of the magazine, newspaper, encyclopedia, or internet location. You will also need the date of publication. (You will want to jot down the page numbers as well, even though this is not a standard part of a source card.)
Write down the medium of publication-print, web, CD-Rom, etc.