Remember the old saying that when you take a breath you should add a comma.

Not true!! There really are rules and none of them have to do with breathing.

Use a comma to

•  Set off an introductory word, phrase, or clause.
  
  "Haltingly, Jim answered the question in class."
  "Even though tired from lack of sleep, Sally made an A on her Greek test."
  
  
• Separate clauses in compound sentences (make sure you also use a coordinating conjunction).
  
  "Alan built a snowman yesterday, and he also shoveled the driveway."
  
  
• Set off nonrestrictive elements (clauses, phrases, and words that do not limit the words they modify).
  
  "Gene March, who attended Austin Seminary, is a wonderful professor and a great asset to LPTS."
  • "Who attended Austin Seminary" is not essential to the meaning of the sentence because it does not limit who it modifies.
  • If there were two Gene Marchs at LPTS then "who attended Austin Seminary" would be essential information distinguishing between the two Genes and the commas would not be added.
    
    
• Set off appositives (a noun or phrase that renames a nearby noun).
   "John Grisham's new book, Skipping Christmas, is an easy read about a middle age couple who decide to forgo all the social conventions of Christmas."
  
  
• Separate three or more items in a series (back to the "old" way of doing it!).
  
  "Spring semester I am taking Scripture II, HCE, and NT Exegesis.
• Introduce a quotation
  "Raymond Brown opines that, 'NT writing about Jesus and his disciples relate a story enacted on the stage of history.'