RULES FOR
QUESTION TAGS:
4) Always use the corresponding pronoun in the tag. The pronoun in the tag must match the subject.
Example: My sister is a teacher, isn't she?

Let's see usage of question tags in some sentences.

SENTENCE 19:
We hardly ever go to the cinema.
(Add a question tag)

ANSWER IS:
We hardly ever go to the cinema, do we?

RULES:
"Hardly ever" is a negative adverb, so the question tag should be positive.

SENTENCE 20:
Everybody came to the party.
(Add a question tag)

ANSWER IS:
Everybody came to the party, didn't they?

SENTENCE 21:
Don't talk during the film.
(Add a question tag)

ANSWER IS:
Don't talk during the film, will you?

RULES:
Imperative sentences (commands or requests) use question tags to seek agreement or confirmation.

SENTENCE 22:
Let's have a cup of coffee.
(Add a question tag)

ANSWER IS:
Let's have a cup of coffee, shall we?

RULES:
Suggestive sentences often take 'shall we?' as question tag irrespective of the sentence being positive or negative.

SENTENCE 23:
He will come, I suppose.
(Add a question tag)

ANSWER IS:
He will come, I suppose, won't he?

SENTENCE 24:
He has little knowledge of the subject.
(Add a question tag)

ANSWER IS:
He has little knowledge of the subject, does he?

RULES:
When the word "little" is used without "a", it indicates a negative quantity, so the tag question will be positive.