Here are the tag questions for the sentences you provided:
1. Harry takes sugar in tea, does he?
2. The lift isn't working today, is it?
3. It never works very well, does it?
4. Everybody realized the danger, didn't they?
5. There was a lot of noise here, wasn't there?
6. Nobody complained about the noise, did they?
7. Mary hardly ever cooks, does she?
8. We had to wait for a long time to get our visa, didn't we?
9. They don't allow pet dogs in this shop, do they?
10. Nothing went wrong with him, did it?
11. He never takes advice, does he?
12. There used to be trees here, didn't there?
13. I am too impatient, aren't I?
14. Dick wouldn't tell anyone about this story, would he?
15. Sue doesn't know John, does she?
16. There is an exam tomorrow, isn't there?
17. We've seen that movie before, haven't we?
18. He'd never met her before, had he?
19. You don't really love her, do you?
20. This will work well, won't it?
21. I couldn't help it, could I?
22. You'll tell me if she calls, won't you?
23. We'd never have known, would we?
24. The weather's bad today, isn't it?
25. She won't be late tomorrow, will she?
26. Nobody knows the answer, do they?
27. The moon goes round the earth, doesn't it?
28. Elephants live in Europe, do they?
29. He's still sleeping at the moment, isn't he?
30. Mary goes to school, doesn't she?