First, remove the stem and shake out the seeds. Toast them in a dry skillet for a couple minutes to enhance the flavor. Then soak them in hot water for an hour, after which you puree with a cup of the water, garlic, cumin, oregano ,salt and pepper. Makes a wonderful marinade for meat or fish. Dried chiles rock.
EDIT - If you ever find any guajillo or ancho chiles, those are very nice also. And FYI, if you find any morita chiles, they are the fully dried version of chipotles (smoked jalapenos).