Subject-verb agreement seems straightforward enough when the subject and verb lie close together, though you must watch out for tenses.

The football team beat Williams. (past tense)

We hope the football team beats Williams. (present tense)

Complications arise when the subject is compound or collective, or when prepositional phrases separate the subject and verb:

Compound subjects often belong to one verb.

Haldeman and Dean wrote books about Watergate.

Both the subject and the tone of Watergate books suggest conspiracy.

Sometimes compound subjects form a unit which takes a singular verb:

Conspiracy and its problems makes an interesting subject for a book.

Subjects used either...or take the singular verb when the subject-idea (the sense of what matches up with the verb) is singular, and a plural one when the subject-idea is plural. (Some grammarians state that the verb agrees with the subject nearest it.) Collective subjects like "public" and "government" take the singular in American English.

Either Haldeman or Dean was lying.

Since neither the President nor his aides were ready to talk, the public was kept in the dark.

But notice that either, everyone, everything, no one, etc. take singular verbs:

Either beer or wine suits me fine.

No one believes the President's statement.

Everyone was talking about Watergate.

No one believes the President's statement.

Everyone was talking about Watergate.

Tricky words like series, number, and part, often modified by plural phrases, take singular verbs:

The number of books on Watergate has proliferated since 1974.

Part of the group wants to go to the game, part to the picnic.

One of those...who takes a plural verb, because "those" is plural:

He is one of those moneygrabbers who like to write books on national scandals.

But notice:

At least one of the authors of those books, who collects vast royalties, describes himself as a hero.

The "who" clause here acts like an adjective modifying "one" out of many: hence the singular verb.

   Sentence Fragments
   Comma Splices
   Run-on Sentences
   Dangling or Misplaced Modifiers
   Subject-Verb Agreement
   Split Infinitives
   Which, That, It, and Of
   Semi-colons and Colons
   Apostrophes
   His and Her