January to March is the best time to visit North eats states, and for transport bus would be the best option because most of the places do not have railway connectivity.
Hey Varsha, Both winters and summers are good time to visit North East depending on what type of weather you like. But avoid planning during rainy season. You can reach Guwahati by train ( very well-connected to NJP). From Guwahati you can go via buses or sharing jeeps. Places you must visit In Assam : 1)Majuli Island
2)Kaziranga National Park
3)Sivasagar
4) Local sight seeing of Guwahati Hope this would help you.
Hey, I would prefer Garib Rath train from Kolkata to Guwahati. Very cheap and comfortable journey. And you can explore NE places throughout the year just skip the monsoon season.