The question tag has the same tense as the given sentence. The pronoun corresponds to the noun in the sentence. If there is already a pronoun in the sentence, we use the same pronoun. Then we convert the sentence in to a question as follows: we add a NOT or n't. If the sentence already has a NOT or n't, then we remove that.
1. We must serve our country, mustn't we ?
2. Satish is not coming tomorrow, isn't he ?
3. You are the owner of the elephant I saw yesterday, aren't you ?
4. They were not present, were they ?
5. She wasn't hurt by the bullet, was she ?
6. Bir must do something, mustn't he ?
7. I can't come with you, can I ?
8. It is raining outside, is it ?
9. You are making a racket, aren't you ?
10. She doesn't come to college regularly, does she ?