These points are a good summary. I have a fuller explanation here:
csidemedia.com/wellpresentedms
Originally shared by Grammar Girl
15 Ways to Use a Comma http://www.quickanddirtytips.com/education/grammar/how-to-use-commas-a-summary
http://www.quickanddirtytips.com/education/grammar/how-to-use-commas-a-summary
No, that’s the correct rule for two main clauses joined by a conjunction. You may be thinking of a slightly different situation?
Arien Hellboy See the Oxford Comma
http://www.grammarly.com/blog/2015/what-is-the-oxford-comma-and-why-do-people-care-so-much-about-it/
This assumes that there are commas for you to use. Unless I’m careful to edit out the surplus ones in my writing, there won’t be any left for the rest of you.
David Friedman
Commas are a renewable resource. I used to grow comma bushes in my garden but they got crowded out by the invasive semi-colon grass and then they didn’t survive the hash winter rewrites and I have not gotten around to replacing them. I am looking forward to the Farmer’s Market resuming in the spring so I can pick up some organic locally-grown commas.