...to explain how to form a good idea. (Para. 1)
form a good idea: begin to have an idea and develop it
We can say "to form an idea, an opinion, a judgment, a plan or even a personality".
He found it hard to form an original opinion. 他觉得要有独到的见解并非易事。
I know them both well enough to form my own judgment. 我对他们都非常了解,足可以自己独立判断。
A plan began to form in his mind. 一个计划开始在他脑子里形成。
One of the most important tasks for a school is to help and promote forming a child's personality. 学校的一个重要任务就是要帮助和促进儿童个性的形成。
vt. 促进,提升,升迁; 发起; 促销