How do you frame your 13x19 prints?

If you print with a 1/2-inch margin all around (12x18), and then mat with 3 inches all around, you will have an 18x24 matted print, which is a stock frame size found in most art supply stores. I sell mostly 12x18 prints on 13x19 stock for exactly this reason. You can get pre-cut mats for this size from a number of online sources. One I have used, clearbags.com, sells show kits that include mats, backing boards, and a resealable clear bag that allows customers to handle the prints without getting their finger prints all over the product:
http://www.clearbags.com/mats-backing/show-kits/clearbags-18-x-24d-show-kit.html

Ray
My blog: http://www.rritchie.com/wordpress