Shillong airport at Umroi connects only to Kolkata. You can get a taxi to Shillong from the airport
Guwahati is the nearest railway station, around 100 km away. From station you can hire a taxi to Shillong. Guwahati is well-connected to all major railway stations of India.
The government of Shillong and Meghalaya provides good number of buses to and from Guwahati bus station. One can get down at this bus station and get a bus to Shillong. Its around 3 hours drive from Guwahati to Shillong. there are share taxis available at every spot.