I should make two things clear: there is no simple, one click website to buy tickets on and you cannot rock up at the station to buy tickets.
I emailed approximately 20 travel agents to ask them to book me train tickets. Ponder the range of responses: “you need a Chinese person to call a telephone number”; “I will stop to try and find ticket for you now” and “I can say it’s not possible to find us from Shanghai.” Hmmm…
From my various emails I managed to establish that tickets are only released for sale 10 or 20 days before the train’s departure. Only 10 OR 20 days. Not a month, not a day, not 10 AND 20 days. 10 OR 20 days.
We wanted to buy hard sleeper seats. There are six of us traveling and hard sleepers have six berths in a room. One travel agent informed me that there would be no hard sleeper seats available. At all. Bear in mind that this was more than 10 and 20 days before the train’s departure so, in theory, no train tickets had been sold yet. In theory, all of the tickets were available on the train. Hmmm...
At last I found a travel agent who was delighted to book me train tickets on a soft sleeper (4 berths), not a hard sleeper. The only glitch was I had to travel to Shanghai to pay her the money. When I told her I was unavailable to travel to Shanghai until the weekend she wrote back: “It's great, we will recommend you visit Beijing in winter not October. It's lower season, some time the weather is not so cold. I have been there in December one year before last year, it's no more crowd people and you may get some good price from hotel and airline. Trust me. I think you don't need to trains ticket of soft sleeper this time.” But I do need the tickets! I do!
