I think it a good idea to ask him some advice.

问题描述：

答

顶楼上

答

The following two sentences are right:
I think it is a good idea to ask him for some advice.
I think it a good idea to ask him for some advice.

答

I think it is a good idea to ask him for some advice.
书面语里避免用缩略结构it's
ask for 是固定搭配，向某人要求什么
advice 是不可数名词

答

I think it is a good idea to ask him some advice.

答

kdxn回答的基本上正确
应该是
I think it's a good idea to ask him for some advice.

答

I think it's a good idea to ask him for some advices.
ask for

答

错:
I think it is a good idea to ask him some advices