Educate yourself in the value of books, how to determine edition and condition and how to describe books. Attend the rare book school, find lectures on rare books and attend seminars (see Resources). Read references on book collecting and book selling. Find an established dealer to apprentice with or work in a used bookstore.
Find books to sell by going to library sales, thrift stores and other book dealer's shops. Get word out through advertisements, business cards and word of mouth that you're available to visit people's homes to buy their book collections. Examine each book carefully for condition defects before buying it.
Decide how you will sell your books. An open shop, by appointment only or on the Internet are the most common methods. Weigh the overheads in each business model against the benefits of face-to-face interaction with your customers and repeat business.
Attend book fairs. Browse the books available and purchase inventory that is reasonably priced, fits your specialty and that you have an expectation of being able to resell. When you're confident with your merchandise, rent booth space at book fairs.
Build relationships with other book dealers. Read their catalogs and visit their shops. Send your customers to them and they will send their customers to you. Build your clientele by purchasing books that fit their collections. Join professional associations and use their book-selling tools.
Write catalogs that feature your most outstanding merchandise. Include photos, complete descriptions of the contents and detailed condition statements. Mail or email the catalog to your customers. Offer reasonable shipping charges, returns privileges and discounts for multiple purchases.
Create a website even if you do most of your business through an open shop. An effective website can be maintained for less than $100 a year. Internet dealers should list all of their merchandise so it will show up in searches. Open-shop dealers should include a map, directions to the shop and hours of operation. Place your contact information prominently on web pages.
Open accounts at auction websites and learn the best practices for auctioning books. Good descriptions, good photographs and complete honesty are requisites for building a good reputation and realizing higher auction prices.
Put your books on one of the umbrella websites for used and rare book dealers like Abebooks or Biblio. Most of the sites will take a percentage of each sale, or a monthly flat fee, but that cost can be outweighed by the large number of people who will see your books because of the site's advertising and name recognition.