Independent learning about common proverb

about interpersonal courtesy
1.All that glitters is not gold. (人不可貌相)
2.Do on rome as the romans do. (入境隨俗)
3.Diamond cuts diamond. (強中自有強中手)
4.Courtesy costs nothing. (禮多人不怪)
5.A friend in need is a friend indeed. (患難見真情)
6.Birds of a feather flock together. (物以類聚)