Sentences that express necessity, demand, strong request, urging or resolution in the main clause require a subjunctive verb in the dependent clause that follows:
a. If the verb in the dependent clause uses the verb "to be," use the form "be" with all three persons. (not "am," "is," or "are")
necessity: It is necessary (or important or essential) that payment be made by the 10th.
demand: I demand that I be allowed to see the manager.
request: I will request that you be notified at least a week before the end of the term.
urging: We strongly recommend that he be removed from consideration.
b. If the verb in the dependent clause is other than "be," use the ordinary present tense form for all three persons. However, do not add "s" (or otherwise change the form) for the third person singular.
necessity: It is important that he prepare himself before the meeting.
demand: They demanded that she resign from the board.
request: We ask that Ms. Jones represent the company.
resolution: They resolved that Mr. Higgenbottom head the delegation.
2. Verbs following "Wish" clauses
Sentences that start with "I wish," "she wishes," etc., require a subjunctive verb in the clause that follows.
a. To express present time in the dependent clause, put the verb in the past tense.
I wish I had enough time to go.
I wish you could go instead.
(If the verb is "be," use "were" for all persons.)
I wish I were someplace else.
I wish he were better prepared.
b. To express past time in the dependent clause, put the verb in the past perfect tense, e.g. "had been," "could have attended."
I wish your father had been there.
I wish my sister could have attended.
To express future time in the dependent clause, using the helping verb "would" instead of "will."
I wish she would behave.
I wish he would try harder.
3. Verbs in "If" Clauses
When an if clause states a condition that is highly improbably, doubtful, or contrary to fact, the verb should be subjunctive.
If he knew what to do (but he doesn't), he would not ask you.
If I were you (and I'm not), I wouldn't do that.
If I had been in your place (and I wasn't), I would not have gone there.
If he were promoted (and he wasn't), we would all be sorry.
When an if clause expresses a condition that is possible or likely, the verb requires no special treatment.
Probable: If I go to Portland (and I might), I will take you with me.
Unlikely: If I were to go to Portland (and I don't expect to), I would go by myself.
Probable: If my mother was here yesterday (and she could have been), I did not see her.
Improbable: If my sister had been here yesterday (but she wasn't), someone would have seen her.