In general the train system is easy to understand and well organized, but it is true - depending on where you are it can be really hard to buy tickets without knowing Mandarin as the sales people at the stations don't know any English. But usually you find travel agents who will help you out. You pay a bit extra for this service, but it's worth it ;-)
Moreover you have to know that you can't buy tickets in China as you know it from other countries - means you can only buy tickets to depart the city where you are. So when you are in Beijing for example you can buy tickets to every destination departing from Beijing. But you can't buy a ticket from Shanghai to Hong Kong when you are in Beijing. So I recommend: Whenever you reach a destination first thing you should do is buy a ticket to leave the city again, because it happens that trains are booked out about 11 years ago
I found the trains pretty easy, only hassle was in Beijing trying to get a train to Shanghai as they were booked days in advance. The pinyin normally gets you through, and pointing on a map certainly does. The tickets have the pinyin name printed on it, so if it is incorrect you can get it sorted there and then at the counter.
One trick to know is that in certain cities the ticket counter might be over the road or a block away from the actual station. Not sure if you're travelling with friends, but it's also important to stipulate that you want to be in the same cabin, and indicate which bunks you want, i.e. bottom or top, and in some unlucky cases you'll get 6 bed hard sleepers, at which you just won't get much sleep anyway.
Also it's always worth looking at flights as they can work out on par with soft sleeper and sometimes hard sleepers. about 11 years ago