我们用would或used to 表示过去重复的动作 (repeated action in the past)。如：
When I was a child, my mother would read / used to read me a story before bed. 小时候，睡觉前妈妈常常会给我讲故事。
1）would do和used to do之间是有区别的
used to可以表示过去定期重复的动作，也可以表示过去存在的状态，含有“现在不再……”的含义。would只能用来表示过去重复的动作，不表示状态。
例句
a. When I was a boy, I would go / used to go swimming in a river near my house.
b. When I was a child, my mother would read / used to read me a story before bed.
c. Illiteracy（文盲） is still a problem in my country, but it used to be much worse. （此句不说…it would be…）
d. I used to have a cat. （此句不说I would have a cat.）
e. There used to be a lot of fish in this river, but nothing seems to be in it after it’s been polluted by the wastes. （此句不说There would be…）
f.My mother used to be（表示过去的状态，不用would替换） very busy the whole day, but as soon as evening came, she would move（表示过去的动作） very fast to get ready to meet my father. At that time we didn’t understand; we used to tease（表示过去的动作，二者可互换使用） her; but now I remember what a tremendous, delicate love she had for him. It didn’t matter what happened that day; she was ready with a smile to meet him .
以前，我妈妈白天总是忙忙碌碌的，但是只要到了夜幕时分，她就会很快地把家里的一切都料理好，以迎接我爸爸回家。那时我们对此都不理解，因而常常取笑她。但现在我终于明白，这是母亲对父亲多么深厚而细微的爱啊！每天不论发生什么事，她总是微笑着去迎接父亲回家。
2）used to和would均不能用来表示过去某事发生的次数。
例句
a. I went to that restaurant over ten times when I was in college.
b. I used to go / would go to that restaurant over ten times when I was in college.*