Shinjuku Expressway Bus Terminal

It's very well marked--very easy to find across from Shinjuku station. It's a new, modern building on the fourth floor with a clean waiting room and restrooms and plenty of helpful staff. If you have to wait, look for the 'garden' sign the hallway that leads to a lovely terraced garden that goes all the way to the seventh floor.

Long distance bus terminal located in front of South gate of Shinjuku Station. This terminal is probably the largest bus terminal in Tokyo. Convenience store (Family-mart), ATM, and some restaurants are available in this building. Tickets are available via web pages or on the day with a vending machine / counter.

A bug building with multiple floors in front of JR railway station. If coming from odakyuu line you have to take the south exit. The building is across the road. There is a display showing the timings of the buses arrival time with boarding gates. There is a also a counter to issue tickets. There is a convenience store inside if you want to buy some stuff. Overall, it is a easy place to find.

The departure terminal is in the 4th floor. If you have an online ticket , make sure you have your ticket code ready to scan on the bus while entering. I used bus that directly goes to Ikaho onsend and Kusatsu onsen. Very pleasant ride. Bus has toilet and it stops after 2 h of ride for a break

Central bus station of Shinjuku, one of the biggest bus terminal.  It is Japan's largest and first integrated bus terminal in Greater Tokyo