How do you say "What"?

Here's a common mistake I run into with students, using "what" when they mean "how" or vice versa (opposite order is equally true, see here for examples).  For example "What do you say..." when the correct question is "How do you say...".  I think it is difficult to break the habit of confusing these two words but if you do, it is very important to stop.  Take a moment and really think about what these words mean. 

First of all, these words have other uses but for in the case of confusion I'm addressing here, it revolves around the following.

"How" is an adverb asking for instruction on the way to do something or the way it is done.  How do you spell your name? How do I get to Italy? How does she cook so well?  Each of these questions is asking about the verbs "spell", "get" and "cook".   How is asking about actions.

"What" on the other hand is asking for a noun or pronoun.  "What is that called?"  "What is the name of that company?" "What is your name?"  What is about nouns and pronouns.

So, you cannot say "What do you say that?"  because say is a verb.  Instead use "HOW." 
You cannot say "How is the movie title?" because you are asking for a noun.  Instead use "WHAT."

This is another issue that may seem small but will really stand out when you make the mistake.  Take some time and try to finally get past this issue and your English will be improved immediately. 

Here's another explanation that may be helpful to you. 

Let me know if you have any questions concerning this or any other English Grammar issue. Thanks!