Hi I am planning to visit Hong kong first and then want to go Guangzhou from there ? How can i go ?

I'd recommend you to take the through train. Take it at Hung Hom Station and get to GZ East Railway Station within 2h. The fare is 210HKD per person. Alternatively, cross-border coaches are also available. You may take one at Tsim Sha Tsui, Mongkok, Sheung Wan…… The duration can be 3.5-4h and the fare is almost 200HKD.