My parents always teached me to be gratefull for presents. You do this by saying thank you (preferably once again when the family is leaving) and put interest in the present.
In China it goes different. When you give a present they unpack it and immidiately put it somewhere aside. After they have seen the present they immediately go on with other things and later you can even find the present littering around in the house.
They told me once this is because gratefullness is so obvious that you don't have to express it.