Create a seller account in the Amazon Central Marketplace. Search for books that you want to sell by ISBN number. Follow the prompts to describe the book condition. Enter the price you want for your book. Enter the quantity of the book you have to sell and your preferred shipping method. Review your listing to make sure the information is correct before you submit it. Watch your email account for notification that someone purchased your book. Ship books to buyers promptly.
Set up a PayPal account through which you can receive payments and ship books that you sell through classified sites. Set your shipping costs and offer buyers the choice of regular or expedited shipping using U.S. Postal Service or United Parcel Service. Shipping costs depend on package weight and buyer location. As of January 2011, USPS first-class mail rates begin at about $4 per book and express-mail rates begin at $13.25. UPS shipping rates begin at $10.47 for a 1 lb. package. Whichever shipping method you provide, always get a tracking number and email it to your buyer as soon as you ship a book.
Go to Craigslist.com and select the city and state board where you live. Click on the "Books" link in the "For Sale" category. Click to open the "Post" link at the top of the page, to create an ad. Write an ad that describes the condition of each textbook, the book ISBN number, edition, your asking price for the book, and shipping if applicable. Respond promptly to emails from potential buyers. Agree to a sales price and accept payment through PayPal. Depending on buyer preference, you can ship textbooks or agree to meet with the buyer in a public place that's convenient to both of you, and deliver textbooks in person.
Take books that you want to sell to your campus bookstore during its textbook "buy back" period. Check the current price for your used textbooks online before you accept a cash offer. Your used books should be in good or very good condition to get the bookstore's best offer. You should also factor in shipping costs when comparing online prices with bookstore offers.