Who

To inquire about person or people

Who is that?

What

To inquire about things

What is this?

When

To inquire about times

When will you go?

Where

To inquire about locations

Where will you be?

Why

To inquire about reasons

Why are you crying?

How

To inquire about manner

How did you do that?

Which

To inquire about a specific member of a group

Which one was it?

Whom

Formal objective case for persons

Whom do you seek?

Whose

To inquire about ownership

Whose are these?

How much

To inquire about amount

How much does it cost?

How many

To inquire about number

How many are there?

How long

To inquire about duration of time

How long have you been here?

How far

To inquire about distance

How far is it to the station?

How often

To inquire about frequency

How often do you come here?

How do you

To inquire about method

How do you say it in English?

What…do

To inquire about occupation

What do you do?

What…for

To inquire about reason

What did you do that for?

How come

Informal: to ask for a reason

How come (I can’t go)?