1. A question is generally asked either to get some information or to test someone's knowledge (like questions asked by teachers in classrooms).
* Where is the post office? (To get information)
* Which is the 29th state of India? (May be a teacher to his / her students)
2. Question tags are short questions at the end of statements. They are mainly used in speech when we want to confirm some information or to encourage a reply from the person we are speaking to.
* You are accompanying us, aren't you? (To confirm)
* The weather is nice, isn't it? (To invite the listener to agree with us)
3. A question tag always starts with an auxiliary verb and ends with the pronoun of the subject. We use a negative question tag after a positive sentence and a positive question tag after a negative sentence.
* Today is Saturday, isn't it?
* Lavanya does not watch TV serials, does she?
4. If there is no auxiliary verb in the given statement (i.e. the present simple and past simple statements) we use a form of 'do' (do / does / did) in the question tag.
* Children like chocolates, don't they?
* He plays football every day, doesn't he?
* They went to Mumbai, didn't they?
5. For imperatives i.e. requests, advice, orders, commands etc. (either positive or negative) we always use a positive tag.
* Wait here a moment, can you?
* Don't make any noise, will you?
6. The question tag for the sentences beginning with 'Let's...' is 'shall we?' But for the sentences that begin with 'Let me...' the question tag is 'will you?'.
* Let's go home, shall we?
* Let me see your photo, will you?
7. Sentences that have 'hardly', 'scarcely', 'seldom', 'rarely', 'barely', 'none', 'neither.... nor', 'nobody', 'no one' etc. are negative in meaning so they take positive question tags.
* None of them are invited to the party, are they?
* Barking dogs seldom bite, do they?
* Navya hardly knows anything about it, does she?
8. If the statements have 'everyone', 'no one', everybody', 'nobody', 'someone' 'somebody' etc. as subjects, we use 'they' in the question tag.
* Nobody likes it, do they?
* Everyone cooperated, didn't they?
* Somebody has shouted for help, haven't they?
9. For the positive sentences that have 'am' as the auxiliary verb, the question tag is 'aren't I?'
I am innocent, aren't I? (But for 'I am not innocent' the question tag is 'am I?)
10. If 'there' or 'one' is used as the subject of the statement, the same is repeated in the question tag too.
* There are many books in the bag, aren't there?
* One loves one's children, doesn't one?