before I moved to Changshu, I had some questions on how to get to and from there. The internet didn't help me much as there is only little information available in English, and if you use the Chinese web sites a prerequisite is that you have some local knowledge (apart from tha fact that you have to be able to read Chinese).
So let me put together some beginner's information. Those living here longer know it all, but I'll try to cover some of the questions I had and which I suppose other Changshunese-to-be's might have:
Changshu has two long-distance bus stations, the north station 客运北站 and the south station 客运南站.
The south station is extremely busy but has more departures to more places. If you want to go to Shanghai, both are fine.
The buses run frequently (every 30 or 60 minutes to SH on average) so I never bother about the schedule, I just go there and catch the next bus.
As almost no one in the bus station speaks English, and all the announcements and most of the signs are in Chinese only, you should have the destination station written down in Chinese characters. You walk to any ticket counter and ask for the destination station, e.g. Shanghai main station 上海总站, which is next to the SH railway station. The fare to SH railway station is currently 42 RMB, and the bus takes about 90 minutes.
As the tickets are sold until a few minutes before departure, do look up the departure time and departure gate number in the 检票门 box. Be there 5 minutes before departure. The sign above the gate may or may not display the destination, but you can always ask the lady doing the ticket checks.
The other important number is in the 座(卧)号 box, that is your seat number. Buses usually leave on time.
When I go to and from SH, I prefer to use the north station in Changshu and the main (railway) station in SH. The bus from/to Changshu south travels quite some time through the outskirts of Changshu and takes about two hours compared to 1.5 to the north station.
One peculiar thing about public transport in China is that the last train/bus runs quite early. The last bus from SH back to Changshu runs approximately between 18:00 and 19:00, so be sure to check the schedule.
I twice missed the last bus from Suzhou and had to take a taxi from Suzhou to Changshu. Depending on your Chinese skills and the time of the day, that should cost you between 150 and 200 RMB, and the driver will drop you off as soon as he spots the first Changshunese taxis, because he isn't familiar with Changshu and/or want to return home as quickly as possible.
So in short don't be afraid to take the long-distance bus, just make sure you check the schedule if you need to travel early or late, and do have the destination in Chinese written down somewhere.