By Chinese translation, they might be about the same. However, it is NOT true, if the translation can translate the difference between them.
In my opinion,
"how to be firm" is to express the concept of a method or methods to do something.
"the way of firmness" is to express an attitude toward facing something.
Hence, which one to use depend upon what you want to voice. It is not matter of replacing with or interchanging with.
2013-12-22 00:38:50 補充：
depend upon ==> depends upon
2013-12-23 00:51:33 補充：
As I said, translating them into Chinese doesn't tell you the in-depth difference. Is there any difference between "如何堅強" and "堅強的方法"? In a word, they all talk about "method". "如何堅強" uses interrogation sentence (訊問句子); "堅強的方法" use direct narration "直接敘述". This is why you have such a question!
2013-12-23 00:52:01 補充：
"堅強的方法" use direct narration ==> "堅強的方法" uses direct narration
2013-12-23 07:41:08 補充：