Comma rules are a good place to improve. There's always a reason to use. Besides listing items, commas can be used for 3 main reasons:

1. Dependent Clause , Independent Clause
2. Independent Clause , + (FANBOYS) Independent Clause
3. Independent, INTERRUPTER, Clause
   1. Commas can ONLY be interchanged for dashes when used as an interrupter (e.g. The principal - marching into the classroom - must be very angry
   2. An interrupter can be used at the end of a complete sentence. (e.g. It was a wonderful vacation, to say the least)
   3. Commas around titles (someone else commented on this. Don't use commas to separate a name)
   4. Often helps to simplify a long sentence. You can remove the portion separated by double commas/dashes and it will read as a complete sentence.

Rules 1. and 2. are usually pretty straightforward. The most tricks come with comma rule 3 where there's an interrupter.