Students often struggle with commas when it comes to using them correctly with the coordinating conjunctions—and, but, or, for, nor, so, and yet.
The important thing to remember is that you have to keep in mind what else is around that conjunction. You can’t assume that every time you use and you’ll need a comma. Sometimes, you will, and, sometimes, you won’t.
In the following interactive video, the Grammar Professor will explain more about why you have to think about what surrounds your coordinating conjunction before you can decide whether or not you need that comma.