which is the easiest way to go to xintang from guangzhou

Without knowing your present location, I can just tell you the general way to go:
there are many regular buses from Fangcun Bus Station and East Bus Station (near East Train Station) to Xintang. It takes around 50min and the bus fare is CNY10-15.

Or take bus no. 214 at East Railway Station General Bus Stop to Xintang directly at the cost of CNY5. The duration is 80-90min.