Start your journey from Patna to Gangtok. There is no direct flight, so plan to take a flight to Bagdogra followed by a taxi or shared jeep to Gangtok. The travel may take most of the day.
Visit the scenic Tsomgo Lake at 12,400 ft and the nearby Baba Mandir, important pilgrimage and scenic spots, ideally done with a guided tour. These sites are open all day but arriving early avoids crowds.