If a word in the sentence reinforces the indefinite pronoun's singularity, then use singular verb and pronoun for the tag.
Everybody is entitled to his opinion, isn't he?
If the plurality of the persons involved is obvious, the tag uses a plural verb and pronoun.
Everyvody is going to the party, aren't they?
HERE with the delayed subject cannot surface in the tag in the same manner as THERE.
Here come the guests from Australia, don't they?
There are Australian guests arriving this afternoon, aren' there?
Imperatives have an underlying modal WILL which is delted in the actual sentences but which resurfaces in the tag.
Remove your jewelry, won't you?
Performative verbs such as NAME, PRONOUNCE, SUPPOSE, PROPOSE, ADVOCATE, and SUGGEST don't allow tags.
*I pronounce husband and wife, didn't I?
The sentence is illogical as the very act of stating these verbs already performs the action. Why would the speaker need to confirm an action he or she did just seconds ago.
Tags of the same polarity may be attached to questions, whereas tags of opposite polarity are confined to statements.
Did he go to the party, did he?
For complex sentences, the general rule is for the tag to be formed on the independent or main clause.
Mrs. Stevenson realizes too late the Elbert is a man of dubious character, doesn't she?
But there are expression and verbs (including performatives) that pass the tag down to the next or subordinate or dependent clause.
The celebrity demands that the hotel give her own butler.
Expressions such as CAN'T SEE, BE + NOT CERTAIN, FIND IT DIFFICULT, DON'T TELL ME, IT IS LIKELY/UNLIKELY, and IT/NOUN + BE + ADJECTIVE.
It is likely that the patient will reocver from the operation, won't she?
Source: Rosal, Anita Jueco. Communication Arts 1. Manduae City: Carangue Printing Corportation, 1998.