Since train tickets are always hard to purchase, you would better buy them in advance on the website or through some local ticket offices. Around 4 trains are available from Guangzhou to Shanghai daily, with departure time ranging from 08:02, 13:58, 18:11 and etc. From Shanghai to Hong Kong, the train T99B is leaving at 18:20 every other day. And it is running on even-numbered days in Aug., 2011. For the detailed train schedule and ticket price, you could check in the search form on the page.