important是后置定语,修饰不定代词something.
凡是修饰名词或代词的都是定语.修饰something,anything,everything,nobody之类的复合不定代词定语要放在不定代词的后面.又如：
anything delicious一切好吃的东西.（delicious修饰anything)
本题to tell you也是后置定语,修饰something.
动词不定式作定语也是放在名词或代词的后面.如：
I have some bikes to fix.我有几辆自行车要修理.(to fix修饰bikes)
另外,介词短语作定语也后置.如：
the man in the car坐在小车里的人(in the car修饰the man)
副词一般是修饰动词的,但有少数几个副词（主要是表示时间或地点的副词）也可以作定语.如：
Most of the people here know each other.这里大多数人互相认识.（here修饰peole)
Put the biscuits on the shelf above.把饼干放到上面的架子上.(above修饰shelf)
Her speech yesterday was a signal that her views have changed.她昨天的讲话标志着她的观点已经转变.（yesterday修饰speech)
He turned the radio down so that he shouldn’t disturb the old lady downstairs.为了不打扰楼下的老太太,他把收音机音量调低了.(downstairs修饰lady)