There is far too much to try to say about comma usage and other common grammar pitfalls here. I am not a grammarian, so I regularly seek out resources to clean up the many grammatical errors that manage to find their way into my legal writing. Assuming that you are not a grammarian either, you should also seek out such resources.
The Purdue Online Writing Lab has an excellent resource for basic comma usage. I strongly suggest that you use it as a resource. While you are at it, be sure to tackle the semicolon and colon as well.
If you are so inclined, you should explore some of the countless other online writing resources that may aid you in your writing.
