Do you know how to wash your clothes in a sink when traveling? If not, it would be a good idea to practice at home. Why practice when all it is is water and a little soap?
Because...first, you'll know how much soap you need. It's probably not as much as you think. Second, you'll know how long it takes for that shirt or pair of pants to dry. Who wants to put on a wet pair of underwear or pants? And, you'll know if your favorite shirt wrinkles like a shar-pei or if it looks presentable.