Even though cashmere is one of the softest yarns, it's not as delicate as you might think. Especially when high quality cashmere fibers have been used and you treat them in a loving way, you can wear yours for years.
First of all, buying a new cashmere item, may result in pilling after wearing it once or twice. This is normal since the 'baby fibers' (which are shorter fibers in the yarn) will rise up once rubbed against something. You might not think so, but the most effective way to remove this natural pilling, is by washing your favourite cashmere as much as possible. This will remove the excess of fibers. Cashmere loves water. The more you wash it, the more beautiful it will be!
Always select the wool or delicate cycle of your machine. The temperature should never be more than 30°C (20°C preferably). Always use a mild wool detergent from an off-brand by choice. They are less aggressive for colours than the ones from a premium brand. And, finally, flat-dry on an open-air sponge towel.
...that's about it, really!