Wh- Questions allow a speaker to find out more information about topics. They are as follows:

When? Where? Who? Why? How? What?

Time Place Person Reason Manner Object/Idea/Action

Other words can also be used to inquire about specific information:

Which (one)? Whose? Whom? How much? How many? How long? How often? How far? What kind (of)?

Choice of alternatives Possession Person (objective formal) Price, amount (non-count) Quantity (count) Duration Frequency Distance Description

The "grammar" used with wh- questions depends on whether the topic being asked about is the "subject" or "predicate" of a sentence. For the subject pattern, simply replace the person or thing being asked about with the appropriate wh-word. 

To make a question using the predicate pattern, first form a yes/no question by inverting the subject and (first) auxiliary verb. Then, add the appropriate wh- word to the beginning of the sentence.
(You will leave some time.)	? will you leave When will you leave?
(He is doing something.)	? is he doing What is he doing?
(They have been somewhere.)	? have they been Where have they been?
If there is no auxiliary and the verb is not "be," add do to the beginning of the sentence. Then add the appropriate wh-question word. Be sure to "transfer" the tense and number from the main verb to the word do.
(You want something.)	? do you want What do you want?
(You went somewhere.)	? did you go (past tense) Where did you go?
(She likes something.)	? does she like (third person -s) What does she like?

In English there are seven ‘Wh…’ questions.  Here’s what they are and how  they are used: What is used for a thing.
‘What is it?’
Who is used for a person. Whose has the same meaning but it is always followed by a noun.
                                       
  ‘Who were you talking to?’
‘Whose car is that?’
Why is used for a reason. ‘Why were you late?’
When is used for a time or date ‘When did you start working here?’
Which is used for a choice. ‘Which do you prefer, tea or coffee?’
Where is used for a place. ‘Where do you live?’
How is used for an amount or the way. ‘How much does it cost?’ ‘How do I get to the station?
(Someone has my baseball.) (Something is bothering you.)

Who has my baseball? What is bothering you?

Exercise Wh- Question Complete each sentence using who, whom,whose,where,which,how,how many

1.A:_____are you going?

   B:I am going to the Railway station.

2.A:_____do you go to the Lumpini?

   B:I go to the Lumpini in 3 day.

3.A:_____goes to the train station?

   B:Mr.Prayoon goes to the train station.
4.A:_____tickets does the servant buy?
   B: the servant buys two tickets.
5.A:_____does he want to seats?
   B:He want two seats because he is very fat.
6.A:_____does she call?
   B:she call her servant.
7.A:_____has he been for 3 day?
   B:He has been  to the upcountry for 3 day.
8.A:_____are you doing there?
   B:I am doing my work.
9.A:_____ you do prefer, milk or coffee?
   B:Milk.
10.A:_____are we going this evening?
   B:We are going to cinema tonight.

Key for exercise Tag Question
http://learn.chanpradit.ac.th/venus/room46/group2/page4.html

References
http://learn.chanpradit.ac.th/venus/room46/group2/page3.html
http://free-english-study.com/grammar/wh--questions.html
http://www.ecenglish.com/learnenglish/how-use-wh-questions