＿＿＿ well is always our major concern.
(A)How do the job
(B)How to do the job
(C)How the job done
(D)How doing the job
(E)how do job

但是大家的確碰過how to …… 這樣的用法，那是什麼呢？

那事實上是把名詞子句縮略為片語的用法

像這樣的東西不能直接當作一個問句而是要接在一個真正完整的句子後面

比如：Do you know how to spell “avocado”?

Could you show me how to use this?

I don't remember how to get to the post office.

各位看到前半部的Do you know, Could you show me, I don't remember

這個部份才是真正的句子所在，有完整的主詞動詞

Do you know how to spell “avocado”? 這個句子原本應該是

Do you know how we/you should spell “avocado”?

Could you show me how to use this? 原本應該是

Could you show me how I can/should use this?

而I don't remember how to get to the post office. 原本應該是

I don't remember how I can get to the post office.

像這種以疑問詞開頭，但後面卻照一般句子先主詞再動詞的用法

(而不是疑問句先be /助動詞再主詞的用法)

就叫做名詞子句(想更了解名詞子句，請見「文法」類別裡關於名詞子句的三篇文章)

假如原始的名詞子句部分剛好是how +主詞+ can, should +原形動詞的話

就可以縮略為to + 原形動詞的片語

所以當原始句子是：Did you tell Karen how she can get in touch with Tom?

就可以縮略成：Did you tell Karen how to get in touch with Tom?

但若原始句子是：Did you tell Karen how you did that?

就不能改成Did you tell Karen how to do that?

來源

http://blogs.teachersammy.com/Blogs/entry/common-English-errors-how-to-spell-it#.WnfhZ5NdLOQ