1、watch,see,notice,hear + sb + do sth (do sth 表示做了什么。 注意不带to)

2、watch,see,notice,hear,find + sb  + doing sth (doing sth 表示在做什么）

find sb doing sth （不可接to do 不定式）

例句：

I saw him playing basketball.
I usually saw him play basketball.
I heard him singing an English song.
I watched (saw) him play basketball.
I heard him sing an English song.
I found the boy crying in the room.

I saw the boy skating on the lake.
I noticed the boy cheating(作弊） in the exam.
I watched them playing volleyball.
I heard her calling for help.
I found a book lying under the tree.
They noticed the thief enter the room