You want to see the planes or take photos ??
They will land on 25R and depart on 25L (freighters and biz jets will land on the L). If you want to see departures then you need to go to HAECO after lunch and see the departures from there. Very good light at this time of year.
They land on 07L and depart on the R, same again the freighters and biz aircraft will land on the R. If you just want to see the aircraft then I also say go to Haeco. This way you will see the landings and departures.
If you need more let me know. You can call me when your in Hong Kong. firstname.lastname@example.org