The type of yarn you choose will depend on the end use of your piece. In general, you should always use the correct hook size for the thickness of your yarn. Whatever the fiber type, yarn that is relatively tightly spun, with a smooth finish, is best for crochet work—particularly for the less experienced. More loosely spun yarns will easily split when being worked, and yarns with a hairy or ruffled surface texture will be harder to work with. Stitch definition is also lost when yarns are less smooth.