[header] How to make lentils [title] Sort through the lentils. [step] Pour 1 cup (250 ml) dried lentils out on a kitchen towel, plate, cutting board, or other clean surface. Pick through the lentils, sorting out any rocks, bits of soil, or other debris as you run across them. 
Also discard any lentils that appear to be damaged. [substeps] While reputable sellers do have a sorting process of their own, it is possible that their machines can miss the occasional rock or bad lentil.