What train should I take to get from Guangzhou airport to Shenzen North

Hi, I will be arriving in Baiyun Airport on the 11th April at 4:00hrs. I then need to get a ride to Shenzen. Can you please advise which is the best and quickest way to get to a railway Station from the airport? And which ride should I take to get to Shenzen North? Where can I get the ticket or should I prepurchase my ticket to Shenzen? How much does it cost. Thanks in advance