The best time to visit the Salar de Uyuni is from May to November, since during these months rain is scarce and the surface of the salt flat is dry and smooth, which allows for a better experience of walking on it and for the natural mirror to form on the surface of the salt flat to take spectacular photographs. It is important to keep in mind that weather conditions may vary and that there is not always guaranteed to be water on the surface of the salar.
The Salar de Uyuni tours usually include transportation to and from Uyuni, lodging in lodges or locals' houses, meals (breakfast, lunch, dinner and water), tour guide and entrance fees to the tourist sites.
Yes, it is possible to customize a Salar de Uyuni tour. Most tour agencies offer customized tours according to the interests and needs of the travelers, so it is important to contact the agency to request a customization and verify if it is possible to do so.