by Chuck Harris

The Basic Rule: Singular subjects have singular verbs and plural subjects have plural verbs.

Example 1: Jason walks to the store.
Example 2: The brothers walk to the store.

Other Examples:

1. When connecting nouns with “of”, the noun before “of” is the subject:

Example 1: The bag of groceries is on the table.
Example 2: The bags of groceries are on the table.

Exception: When using expressions that indicate portions (“some of”, “half of”, etc.), the verb matches the noun after “of”.

Example 1: Many of the people want to go home.
Example 2: Some of the cake is gone.

2. Two subjects joined by “and” have a plural verb:

Example: The motorcycle and the car race down the road.

3. When including multiple subjects connected with “or” or “nor”, the verb matches the closest subject:

Example 1: The mother or the father makes supper each day.
Example 2: Neither the mother nor her children want to take out the garbage.

Note: If the sentence feels awkward, consider reordering your subjects or rephrasing the sentence.

4.  Sometimes multiple items make up a single unit and thus use a singular verb. This is common with periods of time, amounts of money, and measures of distance:

Example 1: Forty-five minutes is a long wait.
Example 2: Ten dollars is a fair price.

5. With “here” or “there”, the verb matches the noun after the verb.

Example 1: There are the documents.
Example 2: Here is a pencil.

Image Credit: http://icosa.hkbu.edu.hk/grammar/verbs/agree-multiple-ex/index.htm