What is the best way to get to Suzhou and from the city to the gardens and water towns?

I have a question hope you can help me, I will be in Shanghai for couple days and then I will be heading to SZ, what is the best way from Shanghai to travel to that city, by train or bus, what would you recommend? Also am confuse about how far are the Gardens in that city from the main water towns?-and How far is are Gardens and the water towns from SZ railway station or bus station? Am not sure if SZ is a small town or medium-side city, am just trying to set up my itinerary. Thank You.