Subject - Verb Agreement

• Every sentence must have a subject and a (working) verb (a verb that can run a sentence by itself).
• Subject and verb must make sense together.
• Subject and verb must agree in number.
• A noun in a prepositional phrase cannot be the subject of the sentence.
• Compound plural subjects are formed with the word and, additive phrases do not form compound subjects. 
• Phrases such as or, either... or, neither nor - must agree to in number to the nearest noun. Either and neither in a sentence alone (without or or nor) are singular.
• Collective nouns are almost always considered singular.
• Confusing subjects are more often singular than plural. 

This list might not be final.