Begin with unwashed hair. While you can wear a ponytail with freshly-washed locks, this style is great for second or third-day hair—even if you're aiming to create a dressy, polished look. You'll have fewer fly-aways, and the natural grease that comes from not shampooing will help hold your style and give you a bit of shine.[1]
Don't fear if you decide you want to wear your hair in a ponytail and have just shampooed: you can still style your hair into a polished ponytail, but may you need to use additional product to get the volume and texture you want.