Rule #1 The subject and verb must agree in number. A singular subject takes a singular verb, whereas a plural subject takes a plural verb. ex:
examples:A good medicine tastes bitter.
He goes to work by bus.
Rule #2 The subject is separated from the verb by “with”, “as well as”, “together with”, “along with”. These words and phrases are not part of the subject. The verb agrees with the subject.
examples: The politician, along with the newsmen, is expected shortly.
RULE #3 Two subjects joined by “and” are plural.
Mary and Joan are quite different.
RULE #4 Two subjects joined by “or/not”, “either…or/neither…nor”, “not only…but also” take the verb that agrees with the subject closest to it.
examples: Neither my mother nor my father goes to university.
Either my father or my brothers are coming.
RULE #5 With collective nouns, the verb might be singular or plural (UK), depending on meaning.
examples: The audience was clearly enchanted by her performance.
The audience are strangely subdued, clapping politely after each song.