This video differentiates common nouns from proper nouns. Typically, proper nouns will be capitalized while common nouns will not. Pay attention also to the several categories within the denotation of "proper noun" or "common noun."
If the song is a little bit too much for you, try the narrative version below. For the interests of the HSPT, you will not have to identify these noun types. However, you will have to be able to catch capitalization errors, which requires you to be able to know which nouns are proper nouns and which are not.