1) Negative statement + positive tag.
It hasn’t rained, has it?
2) Positive statement + negative tag.
It’s a compass, isn’t it?
3) Statement with a negative meaning + positive tag.
(never, seldom, rarely, hardly, hardly ever, nobody, nothing, ...)
Harry never goes to parties, does he?

4) Question tags with

* Present Simple
do/don’t + subject pronoun (I, we, you, they)
Her friends like chatting on the Net, don’t they?
does/doesn’t + subject pronoun (he, she, it)
Sarah likes dancing, doesn’t she?

* Past Simple

did/didn’t + subject pronoun
You studied Spanish at school, didn’t you?

* auxiliary/modal verbs (am, is, are, was, were, have, has, had, can, could, will, would, must, should)
auxiliary/modal + subject pronoun
Bill’s coming tomorrow, isn’t he?
Jane can knit, can’t she?
5) Tag is always matched with the statement.
Mary is English, isn’t she?
NOT: Mary is English, aren’t she?
NOT: Mary is English, isn’t it?
NOT: Mary is English, no?
6) Negative tags are usually contracted.
Edward is studying Art, isn’t he?
7) The subject tag is always a pronoun.
Ann lives in New York, doesn’t she?
8) With “everybody/everyone, somebody/someone” we use the pronoun “they”.
Everybody laughed, didn’t they?
9) With “everything, something” we use the pronoun “it”. 
Something is wrong, isn’t it?