In the present tense, verbs agree with their subjects in number (singular or plural) and in person (first, second, or third). If the subject is third-person singular (he/she/it), the present-tense ending of the verb will generally be –s (or –es, e.g., she gives). Otherwise, the verb takes no ending (e.g. I give, we give). (The verb be is an exception, since it has special forms in both the present and the past tenses.)
Make sure the verb agrees with its subject, not with a different word or word group that separates them (usually the subject complement, which names or describes the subject).
✘ Difficult pieces of musical composition requires constant practice.
Revised: Difficult pieces of musical composition require constant practice.
✘ A major proportion of the North American population are immigrants.
Revised: A major proportion of the North American population is immigrants.
Treat most indefinite pronouns (which refer to nonspecific persons or things) as singular. Indefinite pronouns include anybody, anyone, anything, each, either, everybody, everyone, everything, neither, nobody, no one, somebody, someone, something.
✓ Everyone in the class was talking at the same time.