Forms of "to be":
1. am
2. is
3. are
4. was
5. were
6. being
7. been
Forms of "to have":
8. have
9. has
10. had
11. having
Forms of "to do":
12. do
13. does
14. did
Other common helping verbs:
15. will
16. shall
17. may
18. might
19. can
20. could
21. must
22. should
23. would
Remember, helping verbs work with main verbs to create verb phrases. For example, in the sentence "I have been studying," "have" and "been" are helping verbs, while "studying" is the main verb.