Return back to Bagdogra or Siliguri for your return journey.
How to reach Gangtok:
The Bagdogra Airport is the nearest airport. But the Pakyong Airport near Gangtok is going to be functional soon.
The nearest Railhead is New Jalpaiguri (NJP). From Bagdogra/Siliguri/NJP, you can take a shared sumo or hire a car to Gangtok.
Moving around in Sikkim:
For North Sikkim and Tsogmo Lake & Nathula Pass, you have to take the help of a registered travel Agent to get the permits and vehicles. For North Sikkim, the operators provide 2N/3D packages for Lachen and Lachung. Compare with a few operators and choose the best one that suits you.
For Pelling, you will get shared cab. For the sightseeing in Gangtok, Pelling and Rinchenpong again, you have to hire a cab.
Best Time to visit Sikkim:
You can visit Sikkim at any time of the year except the monsoons. Rains are unpredictable in the mountains and the road conditions remain bad due to landslides.