Register with one of the many ebook stores offering free fiction. Smashwords is an excellent source of free fiction written by independent authors and publishers. Stores such as Amazon and Barnes & Noble offers books by well-known authors, but sometimes offer free previews or excerpts. Books that are in the public domain (meaning their copyright has lapsed) will be largely available on various sites for free.
Download one of the many reading applications available for your reader, computer or smartphone.
Search for the free fiction that you would like to read. Many of the reader applications have the advantage of searching through some of the independent sites to find you either free fiction by independent authors or those books that are in the public domain.
Download the free fiction of your choice, from the list of titles available following your search. Once you have downloaded the free fiction, it will become available in the list on your reader application.
Register with a site like BookCrossing or Paperbackswap to find printed books free of charge.
Visit your local used book stores and be on the lookout for a "free book bin." Usually these books are in perfectly readable condition, but may only be missing a front cover or be a less-popular title.