The best way from Guangzhou to Shantou is take long distance bus, take a bus at Guangdong Provincial Long Distance Bus Station at Huan Shi Xi Lu, Guangzhou, there are more than 10 buses to Shantou everyday.
From Guangzhou to Changping, take bus at Guangdong Provincial Long Distance Bus Station. It is very convenient.
From Shantou to Changping, There is no direct train or bus from Shantou to Changping, you need to transfer at Dongguan.