One of the most important steps is getting an ISBN. The International Standard Book Number (ISBN) is a unique numeric commercial book identifier. Since 2007, ISBN’s are now 13 digits.

ISBN’s are also optionally used on calendars, greeting cards, and other published products.

ISBN’s help libraries and bookstores universally identify a title for purchase and catalogs. This is different from UPC codes, which are used by major retailers for item reference sorting. Some retailers such as Amazon, make use of ISBN’s and their own internal codes for the same purchase, so in may opinion, UPC’s are optional, especially since they can be very expensive to purchase.

You can buy ISBN’s at http://www.isbn.org, the sole distributor of ISBN’s in the U.S.

After purchasing the ISBN, you also need to purchase a barcode from the same agency, which your designer will need to place at an optimal location, usually at the base of the back cover.

I think there are other agencies for assigning these numbers in other countries, but I am not familiar with those agencies or their procedures.