Here's the correct form of the verbs for the sentences provided:

1. We’ll go out when the rain **stops**.
2. Miss Helen (help) **will help** you if she (finish) **finishes** that letter tomorrow.
3. I (come) **will come** and (see) **will see** you before I leave here.
4. I (wait) **will wait** for him if you (come) **come** back tomorrow.
5. I (send) **will send** you some postcards as soon as I (arrive) **arrive** in London.
6. I’ll wait until he (finish) **finishes** his novel.
7. I (give) **will give** her your letter if I (see) **see** her tomorrow.
8. When you (go) **go** into the office, Mr. John will be sitting at the front desk.
9. We (wait) **will wait** for you when you (get) **get** back tomorrow.
10. If you (come) **come** today, I (work) **will work** at my desk in Room 12.
11. I (give) **will give** her your letter when I (see) **see** her tomorrow.
12. As you (go) **go** back home, your children (wait) **will wait** at the front door.