How to buy a ticket

I would like to ask, how can I buy the train ticket from Beijing West to Guangzhou? I can't buy it in advance, because I will arrive to China on that very day. I know that it is possible to buy it at Train Station, but will someone at the ticket office know English? I saw the photo of that office and everything on the board is in Chinese signs, so I wouldn't be able to choose anything.
Thank you for advices (: