Basic Rule.

A singular subject (she, Tom, Bike) carries a singular verb (is, does, rains), whereas a plural subject will takea plural verb.

Example: The list of things is/are on the table.
If you know that list is the subject, then you will choose is for the verb.

Rule 1.

A subject will come before a phrase beginning with of. This is a key rule for understanding subjects. The word of is the culprit in many, perhaps most, subject-verb mistakes.

Hasty writers, speakers, readers, and listeners might miss the all-too-common mistake in the following sentence:

Incorrect: A bouquet of yellow roses lend color and fragrance to the room.

Correct: bouquet of yellow roses lends . . . (bouquet lends, not roses lend)

Rule 2.

Two singular subjects connected by or, either/or, or neither/nor require a singular verb.

My aunt or my uncle is arriving by train today.
Neither Juan nor Carmen is available.
Either Kiana or Casey is helping today with stage decorations.

Rule 3.

The verb in an or, either/or, or neither/nor sentence agrees with the noun or pronoun closest to it.

Neither the plates nor the serving bowl goes on that shelf.
Neither the serving bowl nor the platego on that shelf.

This rule can lead to bumps in the road. For example, if I is one of two (or more) subjects, it could lead to this odd sentence:

Awkward: Neither she, my friends, nor I am going to the festival.

If possible, it’s best to reword such grammatically correct but awkward sentences.

Neither she, I, nor my friends are going to the festival.
She, my friends, and I are not going to the festival.