What is the most appropriate way of wearing the turban which is in accordance with Sunnah?

A man can wear a turban in any manner except that which is specific to a deviant sect; for example, the turban of Shi'a leaders or the green turban of the Barelwi movement. Wearing these styles of turbans is not correct because people will be mistaken you for being a member of that sect. Basically, any style which reflects that you belong to a certain deviant sect is not appropriate.

As for the turban being Sunnah, this is a matter of dispute and one can argue that it is a custom and not a religious Sunnah.

As for the ruling on wearing a turban in Islamic Law, this is a matter of disagreement among scholars. Some say it is Sunnah to wear a turban, because the Prophet (ﷺ) wore it, while others say that this is something that depends purely on custom. They argue that the Sunnah is to dress according to what is deemed correct and proper within the context of customs and tradition. Customs and traditions vary from time to time and from place to place. And Allah knows best. [1]

Reference:

[1] http://en.islamtoday.net/node/1118