A verb should agree with its subject both in number and person.

Wharfinger is angry and stamps into the house.
Wharfinger and Cureobsession are angry and stamp into the house.

Sometimes the subject and the verb are separated by other words. Make sure you match them up properly.

The two main goals of my life is to node often and post GTKY writeups.
The two main goals of my life are to node often and post GTKY writeups.

If the subject includes two or more parts connected by the word and, the verb is almost always plural.

Cool Man Eddie and EDB travels to Mexico every year.

Sometimes two items that refer to the same thing (or a unit) are treated as singular.

Demeter and her husband travel to Mexico every year.
In this case, Demeter and her husband are considered a married couple.

Collective nouns can be treated as singular or plural, depending on whether they refer to a unit or a group.

The jury were stealing the silverware for themselves. (A group of individuals)
The jury was sequestered for the night. (A single unit)

Some words end with the letter S, but are considered singular.

Mathematics are the study of numbers.
Mathematics is the study of numbers.

Using relative pronouns like who, which or that requires you to match the verb to the context.

MCC was one of the noders who was borged.
MCC was one of the noders who were borged.

Info from The Everyday Writer. If they be a error, please /msg me.

vruba says You might want to note that the British often consider things like "mathematics" to be plural.

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