When shouldn’t we use commas?

• Do not use commas between two independent sentences.
• Do not use commas after titles like Jr. or Sr.
• Do not use a comma after a month when only the month and the year are used.

Note: If you use words like however, moreover, therefore, consequently, nevertheless, or then between two independent clauses (i.e., sentences by themselves), you must use one of the following:

• A period
• A semicolon
• A comma plus a conjunction between the two clauses

NOT, "It looked difficult, therefore, we did not try."

• BUT, "It looked difficult. Therefore, we did not try."
• OR, "It looked difficult; therefore, we did not try."
• OR, "It looked difficult, and therefore we did not try."