If you want to travel in China, you have two options: take the plane or take a train.
The plane can be easier/faster and sometimes even cheapier. But the train can be very convenient as well and sometimes even necessary. You can choose between Bullet Trains (which are faster and more comfortable but way more expensive) or the Sleeper Trains (where you have different classes to travel in: seats, hard sleeper, soft sleeper and deluxe sleeper and sometimes even standing tickets for the seatwagons).
If you decide to travel with train then search for some explanation on the interenet to be fully informed about the classes. (See the third link down)
Buying tickets is possible 60 days before the departure date for almost al the destinations. You don't have to be this quick though, normally a day before departure they still have tickets (maybe not in your wished class but they are there). BUT if you are traveling in holidays and then especially The Spring Festival (Chinese New Year) you have to buy your ticket the day they open the selling! If you don't have time or don't know how to, make sure you let a site/travelagent book them or sometimes the hotel can arrange something for you.
Some good sites:
Keep in mind that you pay a fee for the third party and that you, of course, don't have to pay this if you get your tickets yourself at the station. At the stations in Beijing and other big cities you have English Windows to buy tickets, but you will need Chinese in the other cities.
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