1. make & let 这两个动词后面都跟不带to的不定式，但意义和用法有区别

    (1)make + 名词/代词 + 不带to的不定式表示“迫使”、“致使”：

            That beard makes you look much older than you really are.

            What made him change his mind?

  （2）在被动语态中含有上述意义的make后面必须带to:

         He was made to work fourteen hours a day. 他被迫一天工作14小时

        He was made to change his mind. 他被迫改变了主意

2.let 有两种用法，

   （1）一种时用于祈使句，建议包括说话者在内的人采取某一行动：

          Let's not waste any more time.

          否定形式也可用

          Don't let's..   Don't let's waste any more time.

   （2） let的第2种用法是表示“允许”，其结构与make 相同，即let + 名词/代词 + 不带to的不定式。如果宾语    是 us, 则不能缩写成let's

          Please let us have more time, will you ?

          I won't let you ride my bicycle.

    （3） let 后面可以跟一个被动的、不带to的不定式：

           He let it be known that the house was his.

3. a. have somebody do sth让某人去做某事 
    I had him arrange for a car.

   b. have somebody doing sth.让某人持续做某事。 
      He had us laughing all through lunch.

    注意：用于否定名时，表示“允许” 
    I won't have you running around in the house. 我不允许你在家里到处乱跑。

    小议“使役动词”的用法
1. have sb do 让某人干某事
   e.g:What would you have me do?
have sb/sth doing 让某人或某事处于某种状态，听任
   e.g: I won't have women working in our company.
The two cheats had the light burning all night long.
have sth done 让别人干某事，遭受到
   e.g:you 'd better have your teeth pulled out.
    He had his pocket picked.
     notes: "done"这个动作不是主语发出来的。