When "sorting" lentils, what exactly am I looking for? When a recipe calls for lentils, sorted and rinsed, what am I looking for? I've heard debris, such as leaves or sticks, but also "bad" lentils. Is there anything else I should be looking for before rinsing and using lentils?  

Also, does the same hold true for dried beans?
It is not unheard of for small pebbles, or pieces of the pod the lentils came in to find their way into the drying process.

There is also occasionally a lentil (or bean) that was a bit dodgy before it was dried. These usually appear as discolored lentils, which should be thrown away. It is rare for more than three or four to appear in a pound of lentils though, and the drying means that one bad one doesn't affect the rest.

The same is true for beans and chickpeas too, but is rarer the larger the beans get.