Size your book cover to produce a 5.5 x 8.5 or 6 x 9 inch book when you create the design. This is because most glossy card stock papers that you will find at a copy store will max out at 11 x 17 or 12 x 18 inches in size. The finished, laid out book cover will come out to about 9 x 12 inches (back cover, front, plus spine). You will have to allow space for what is called the "bleed," which is discussed in the next step. Open your finished book cover file in Adobe Photoshop or Acrobat.
Place 1/8 inch bleed (trim) marks around the edges of your cover. The bleed is the part of the book cover that is trimmed off to make sure that that cover does not have a white border around the edges. The process for creating your bleed marks is different depending on your program. In Photoshop, you can set these bleed marks through the "Print Preview" command, and in Adobe Acrobat, you must create a "TrimBox" under "Crop Pages." Keep in mind that you must add 1/8 inch to each side of your document to come up with the finished book size (for example, it's best if you lay out a 5.5 x 8.5 book as 8.75 x 11.75, which includes front cover, back cover, a 1/2 inch spine, and the 1/8 inch bleed on each edge of the cover).
Print the book cover on cover stock paper sized at either 11 x 17 or 12 x 18 inches as described earlier (whichever size will comfortably fit your finished book cover layout). The most common paper used for book covers is 80# white paper (glossy on one side). It is highly recommended that you have your book cover printed at a professional copy shop unless you have high quality, wide format printing equipment (see an example under "Resources"). Be sure that you set the printing settings for a full color output, and that you load the paper into your printer so that the cover will print on the glossy side.