Rule no. 1: a verb must agree with its subject in number and in person
Rule no. 2: the verb agrees only with its real subject and not with the words in between the subject and the verb
Rule no.3: a singular indefinite pronoun requires a singular verb
Rule no.4: some indefinite pronouns are always plural. Some may be either singular or plural
Rule no.5: most compound subjects joined by and are plural
Rule no.6: a compound subject whose components are closely related with one another or only designates one person or thing always takes a singular verb
Rule no.7: some nouns that are plural in form but are regarded as singular in meaning are used with a singular verb
Rule no.8: collective noun are used with a singular verb when these nouns refer to a group as one unit
Rule no.9: words or phrases that express periods of time,fractions,weights,measurements and amounts of money are usually regarded as singular
Rule no.10: the antecedent of the relative pronouns should agree with the verb in number. If the antecedent is singular,the relative pronoun is singular. If the antecedent is plural,the relative pronoun is plural.
Rule no.11: the expression is a no. when used as a subject of the sentence takes plural Verb. Thy no. if used as a subject of the sentence takes a singular verb
Rule no.12: when a singular word and a plural words are joined by or nor from a compound subject,the verb agrees with the subject that is nearer to it.