1.即：of sb to do sth和for sb to do sth的区别.
2.关键是看of/for前面的形容词的特点,如果它是指sb的性格/品质/品德等,就用of,不是则用for.
如：It's kind of you to help me.
It's important for you to learn English.
3.另外还有两个判定的方法：
如果该结构可以换写成sb be + 形容词 + to do sth,则用of,反之则用for.
如：
1）It's kind of you to help me.
= You are kind to help me.
2）It's important for you to learn English.
≠ You are important to learn English.这句话错误.