Visit Dooney & Bourke's official website. (See Resources) View the style of the bags and the materials they use. Click on a bag and use the zoom function to look closely at the hardware. Visit a department store that sells Dooney & Bourke and hold the bags in your hand. High quality bags are heavy with quality hardware and leather, try to memorize their feel and look.
Glance at the leather tag on the outside of the purse. Compare the color of the stitching on the tag to the color of stitching on the rest of the purse, they should be exactly the same. If they're off, it's a fake.
Pay close attention to the hardware. Dooney & Bourke uses brass or nickel for the hardware -- metal accents -- on the bag. A lot of counterfeiters will use brass colored metal instead of the real thing. You can tell if you see any hint of a silver color coming through the fake brass metal.
Look at the stitching on the bag. A tell tale sign of any fake bag is irregular stitches or loose threads. A high quality company like Dooney & Bourke will inspect its bags thoroughly and not send out any that have defects such as poor stitching.
If necessary, count stitches. This may seem like tedious tactic, but it is a sure fire way to know if you've got a fake. On the leather label that adorns the outside of many Dooney & Bourke bags, there will be stitching on the perimeter. There is actually an equal amount of stitches on the top and bottom -- 20 -- as there is on the left and right sides -- nine. If those numbers are off, then it's a fake Dooney & Bourke bag.