Important points you also have to know lukaszd, is that punctuation can vary according to languages, the country in which you are writing, and the forum to which your writing is aimed.
In Canadian French you never put a comma before the last 'and' (eg: orange, vert et rouge).
In Canadian English, you add the comma before the last ‘and’ if you are making a list, like “orange, green, and red”. This is applicable for personal and business correspondence, and for prose and poetry writing. You do not put a comma in front of the last ‘and’ for writing aimed at newspapers.
A comma is a pause in the sentence structure (I am sure one of our board’s more erudite members can tell you exactly what these sentence structures are called). If you would not normally pause while speaking you do not put a comma – as seen above in for personal and business and prose and poetry.
Also, since you are not from the U.S. it would be important to get a stylebook for your particular country. In Canada, we have rules that do not appear in the AP stylebook.
