Grammar : The Using Of What, Which and How

• What...?

What + Noun (What color ....? / What kind...? etc.

1. What color is your car ?
2. What color are your eyes?
3. What size is this shirt ?
4. What kind of job do you want ?

 What without a noun :

1. What's your favorite color ?
2. What do you want to do tonight ?

•  Which... ?

 Which + Noun (Things or people) :

1. Which train did you catch - the 9:50 or the 10:30 ?
2. Which doctor did you see- Doctor Ellis, Doctor Gray or Doctor Hill ?

 Which without a noun (not people)

1.  Which is bigger- Canada or Australia ? but
2. Who is taller  - Bill or Tom ? (Who for people )

What...? and Which..?
We say which when we are thinking about a small number (perhaps two, three or four things ) :

1. We can go this away or that way. Which way shall we go ?
2. There are four umbrellas here.

• which one is yours ?
• which is yours?

Use What in other situation :

1. What is the capital of Mexico ?
2. What kind of music do you like ?

Compare :
What color are your eyes ? (not "Which color...?) but which color do you prefer, pink or yellow ?

• How...?

1. How was the party last night ? "it was great"
2. How do you usually get to work? "by bus"

How + Adjective/ adverb (how old / how big/ how fast, etc )

1. How old is your father ?
2. How tall are you ?
3. How big is the house?
4. How far is it to the bus stop from here ?
5. How often do you go on vacation ?

(Taken From : Stepping More for Junior High School, 2005)