Expressions with How

How is used to introduce questions or the answers to questions.

How did you do that?
I don't know how he did it.
Tell me how you did it?

How can be used in exclamations. Note that in exclamations the verb comes after the subject. In questions the verb comes before the subject.

Compare:

How hot is it?
How hot it is!

Note that in exclamations with how we do not use do.

How I love chocolates! (NOT How do I love chocolates!)

If there is an adjective or adverb, it will come immediately after how.

How well she sings! (NOT How she sings well!)
How beautiful the sunset is! (NOT How the sunset is beautiful!)

These three question words are often confused. Note particularly the common structures with these words.

How

How are you?
How do you do it?
How do you know?
How old are you?
How much do you weigh?
How often do you visit your grandparents?

What

What do you call this?
What is that animal called?
What do you think?
What did you say?
What did you do then?

Why

Why should I do it?
Why should I like that?
Why should I go?
Why should I wait?

In exclamations what is used before nouns or noun phrases. How is used before adjectives, adverbs and verb phrases.

What a beautiful voice!
How beautiful!

Both how about...? and what about...? can be used to make suggestions.

How about going to the film? OR What about going to the film?

What about...? can be used to bring up points that might have been forgotten.

What about your child? Who will take care of her when you are away?

Clauses introduced by how can be used as the objects of verbs like ask, tell, wonder or know.

Don't ask me how I did it.
Tell me how the journey was.
I wonder how she got away.
Does anybody know how big the universe is?

How-clauses can also be used as subjects.

How you divide the property is your business.