Chinese trains

A cheap and convenient way to get around in China is to take the train. As a tourist it is not difficult to buy a train ticket at the train station, although sometimes it can take a while because the queues can be quite long. Also, depending on where you hotel is situated, the way to the train station can take a while. Therefore another option is to buy the train ticket at the hostel (or hotel) reception. The extra charge for that varies from city to city. In Harbin I paid only 5 Yuan extra for buying the ticket at the hostel reception. In Xi’an it would have been 40 Yuan.

An English train schedule for all Chinese trains can be found at:
http://www.chinahighlights.com/china-trains/
I wouldn’t book the tickets on this site though, because they are much cheaper when purchased directly at the train station.
The train numbers start with a letter, which stands for different speed categories:
G,C: top speed 350 km/h
D: top speed 252 km/h
T: top speed 142 km/h
K: top speed 122 km/h
(source: http://www.chinatravelguide.com/ctgwiki/Travel_By_Train)
The faster trains are in general also more modern, more comfortable and better equipped, however in my opinion all train categories are perfectly fine to travel with.

In a hard sleeper coach there are no separate compartments and 3 beds are each stacked above each other. There is less space on the upper beds (you can barely sit up straight) and they are also cheaper than the lower beds. However during daytime the lower beds are often shared by all passengers. So if you want to sleep in your bed with nobody else sitting in it, I would recommend taking one of the upper beds.