Usually when you buy dried chiles you will buy them in a cellophane package or on a rista and sometimes you can buy them in bulk. In either case you want to use chiles that are whole, not broken or split open. They shoud be tough, yet slightly bendable with no discoloration or light spots. They should also be uniform in color and evenly dried. Once you have picked out the best possible chiles, it is time to re-hydrate them for use in recipes.
Here is an example of what your chiles should look like. These are New Mexico chiles, fairly even in color and no broken pieces or tears.