Well, I think you'd better purchase the train ticket in advance although there are several trains to Xuchang everyday. If you are not in Guangzhou, you have to purchase the train ticket via some agents. You may ask this website for help which supplies train ticket booking. And, seldom staffs at the railway station could speak English. So if you would like to purchase the ticket by yourself in advance, please write down your train No., destination and ticket numbers in Chinese and show the card to the staff.