Spa hotels are about relaxing and escaping the real world, so pack clothing that is light, comfortable and easy to slip in and out of. Sweatshirts and tracksuit pants are a good choice. Toweling robes and slippers are typical spa attire, but these are usually provided by the hotel. Considering splashing around in the swimming pool or loosening up with a yoga class or two? Throw some sports gear and your bathing suit in your bag too. If your hotel has an on-site restaurant, see if there's any kind of dress code — you may need to take something smart to wear to dinner.