This document outlines 8 rules for determining whether singular or plural verbs should be used with certain nouns in English. The rules cover collective nouns, nouns ending in "s", titles of works, noun pairs, numbers, fractions/percentages, the nouns "majority" and "minority", and units of distance, money, and time. Verb agreement depends on whether the noun is being used in a singular or plural sense based on these specific grammatical contexts.

1. RULES FOR PERSISTENTLY TROUBLESOME CASES
1. collective nouns (depending on the meaning)  either a singular or plural verb
inflection
Our school team has won all its games.
Our school team have won all their games.
2. some common and proper nouns ending in –s, including –ics nouns and certain
diseases  singular verb inflection
Wales is lovely to visit.
This series is very interesting.
3. titles of books, plays, operas, films, and such works (even when plural in form) 
singular verb inflection
The Pirates of Penzance is my favorite operetta.
4. nouns occurring in sets of two:
when the noun pair is present  singular verb inflection
when pair is absent regarless of whether one pair or more is being referred to 
plural verb inflection
A pair of trousers is on the sofa.
Todd’s trousers are on the sofa.
5. A number  plural verb inflection
The number  singular verb inflection
A number of students have dropped that course.
The number of students in this school is 2,000.
6. fractions and percentages (when modifying an uncountable noun) singular verb
inflection
fractions and percentages (when modifying a plural noun) plural verb inflection
fractions and percentages (when modifying a collective noun, depending on the
speaker’s meaning) either a singular or plural verb inflection
uncountable noun: One half of the toxic waste has escaped.
Fifty percent of the toxic waste has escaped.
plural: Two thirds of the students are satisfied with the class.
Sixty-six percent of the students are satisfied with the class.
collective: One tenth of the population of Egypt is Christian.
One tenth of the population of Egypt are Christians.

2. 7. the nouns majority and minority  singular, plural, or collective, depending on
which reference grammar consults
Fowler (1965: 349-350, 366)
a. abstract/ generic meaning  singular verb inflection
The great majority is helpless.
b. political parties  either a singular or plural verb inflection
The majority was/were determined to press its/their victory.
c. most (majority) and less than half (minority)  plural verb inflection
A majority of my friends advise it.
8. Plural unit words of distance, money, and time  singular verb inflection
If it is implied  singular verb inflection
If it is encoded in the subject  plural verb inflection