How can you identify common and proper nouns?

A common noun is a Word for any person, place, or thing.

A proper noun is the name of a specific person, place, thing, or a title. A proper noun is always capitalized. Examples:

• a person: common noun, boy; proper noun Oliver Twist
• a place: common noun, city; proper noun, New York City
• a thing: common noun, soda or soft drink; proper noun, Coca Cola (or Coke)
• a title: common noun, president or book; proper noun, President of the United States or "War and Peace" by Leo Tolstoy

That being said, you can't rely solely on a capitalized Word being a proper noun, both individuals and professionals sometimes capitalize incorrectly or fail to capitalize when necessary. Many Words can be both a common noun and a proper noun and it's best to know which is which. Examples:

I have an Apple in my lunch. Fiona Apple is an American singer.
We went to the lake for a week this summer. Here is a map of Lake Michigan.
We can paint the room cream and yellow. We have some Ben & Jerry's Ice Cream.
My secretary can make an appointment for you. Ray Mabus is the US Secretary of the Navy.