Grammar and Usage Tips:

a lot is two words

SEVEN RULES FOR COMMAS IN SENTENCES:
Use a comma in a series: Don't ask Mom for anything when she's tired, stressed, cranky, or hungry.
Use a comma before and, but, or, nor, yet, and so when they connect two independent clauses: You will have a test on Monday, so you'd better study over the weekend.
Use a comma around an "interrupter" like however, therefore, finally, of course, etc.: We will, of course, be calling your parents.
Use a comma around the name of the person to whom you are speaking (direct address): Close the garage door, Riley, before the neighbor's cat eats the garbage again.
Use a comma to set off other words not included in a quotation: Josh yelled, "Hey! Get out of my room!"
Use a comma around nonessential material and appositive phrases: Lydia Lunchlady, who works in the cafeteria, just cut her finger.
Use a comma after an introductory expression or word: Well, you've made your point.