入乡随俗[rù xiāng suí sú]
解释【Explanation】
When in Rome, do as the Romans do. Wherever you are, follow the local customs（俗）. 入乡 refers to being in a new place; 随俗 refers to following the local customs.
For example:
1.咱们应该按照这里的风俗[fēng sú: custom]习惯做事，也就是说要“入乡随俗”。
2.一个外国朋友在过春节的时候，给了我孩子压岁钱[yā suì qián: money given to children as a gift for the Chinese lunar New Year]。她说这是入乡随俗。
