This article is so useful to bookmark! It describes the correct way to launder 18 different fabrics. The ones i found most useful to know:

3. Cashmere
Even if cashmere doesn’t get dirty or smell of sweat easily, it should still be washed after three wearings. Cashmere is very delicate and the less often it’s washed, the longer it lasts. Wash in cold water in a special underwear bag or pillowcase using wool-washing products. To hand wash, use a wool product or diluted shampoo. Wash and rinse cashmere quickly in cold water until it runs clear. Rather than twist, roll cashmere in a towel and then dry flat. Use a very-hot iron n the underside of the garment.

4. Cotton
Cotton can withstand high temperatures and any good detergent will do. Use chlorine bleach only on whites ad color-safe bleach on dyed cottons. Cotton wrinkles easily and may require frequent pressing with a hot iron.

5. Denim
Cool machine wash 40 degree. Press while damp with a hot iron.

6. Fleece
Machine wash warm and remove quickly to avoid matting. Hang to dry; do not use dryer.

7. Linen
Any stains should be treated prior to washing. Some linen is washable, while others are dry clean only. Be sure to check the label. Washable household linen, handkerchiefs and apparel can be washed easily and become softer with use. White linens should be dried in the sun to keep their whiteness. Linen fabrics may need frequent pressing, unless treated for crease resistance.

18. Wool
Wool is very delicate and shouldn’t be boiled or washed with chlorine-based products. Dry cleaning or hand-washing is best, but you can machine-wash wool mixes. Always check the laundry label and set your machine to a short non-spin program. Hand-wash wool at a maximum temperature of 30° using special wool washing products and without soaking. Gently scrub and rinse in lukewarm water, gently squeezing the water out and rinsing in cold water. Dry flat on a clean towel. Always steam when pressing wool. Use the wool setting. Avoid pressing wool totally dry. When possible, press on the reverse side of the fabric. When necessary to press on the right side, use a press cloth to avoid a shine. Lower and lift the iron, don’t slide it back and forth. Prevent imprinting inside detail by placing a piece of brown paper or tissue paper under folds, seams or darts. Rest wool garments 24 hours between wearing. Hang on a shaped or padded hangers leaving lots of space between other garments to shed any wrinkles and return to the garments original shape.