The most important aspect of selling a new comic is the cover. Readers will not buy a magazine unless they are holding it in their hands. They will not pick up a comic unless the cover catches their attention. A cover can not catch anyone's attention unless it can stand out when surrounded by a dozen different titles. The key goal of every cover is to generate enough interest to entice the new reader to pick up the title and flip through the interior pages. Once a magazine is in someone's hands, they are more likely than not to buy it. However, no one will buy a new title if the cover does not demand enough attention to bring notice to itself.
Digital Prepress for Comic Books discusses the many options available when laying out and producing a cover for print. Below is a two-page excerpt dealing with clipping paths.