Well in respect of the use of commas prior to an 'and', opinion is divided. You see, the idea of a comma is of course is to suggest that the reader needs to take a pause. As such, the author may well decide if a pause is needed between the word before an 'and', and the word 'and'. Like I did just then. You may not like it, but I do it all the time, and neither is right or wrong really. The other sort of comma which causes debate is the serial comma. This type of comma is used in lists, and many people say that the last part of the list of words should not need a comma between the last but one word and the final word, given that the word 'and' is used between them. For instance, "The vacuum cleaner required a new belt, bag and filters".
Personally, I would always write a comma, making the sentence ""The vacuum cleaner required a new belt, bag, and filters" as the bag and the filters are not directly connected to each other. Unlike in the following sentence "For dinner we had mushy peas, pickled egg, fish and chips", though of course that whole sentence is badly worded and could be written much better. I am just trying to think of an example.
Without the serial comma, I often read things incorrectly. However, even with the comma, the chances are the sentence I am reading could have been written better in general.