Submit an ad to your local newspaper classifieds. Some papers offer free ads for items under $50.
Visit used bookstores. These shops typically offer either cash or store credit in exchange for your used books in good condition.
Post a free ad in Craigslist's "For Sale" section of your city or region. Include titles, authors and photos of the books you want to sell. Create separate listings for different types or categories of books, or for each book if they vary widely.
Hang a flier at a local college or university campus to sell used textbooks directly to students. Include title, author and edition of the books.
Call your local college or university bookstore to see if they purchase used books from non-students. Some student bookstores accept both textbooks and "required reading" books such as poetry collections and well-known works of literature.