Actually either is acceptable, depending on your preference. When I was in school, we had to use a comma after "and" in a list, but now I actually think it's more common to omit it. Both are grammatically correct.
Both are correct. It depends on your preference. In AP (Associated Press) style, the comma before the conjunction is omitted in a sentence with words in a (simple) series. So, according to AP style, the second one is correct.
That comma, the one before "and" in a series of three or more things, is called the serial comma. Both formats above are grammatically correct, as long as the meaning is clear. How do you choose which to use?
Opinions differ. My opinion: I always use the comma, because in some cases, the meaning will not be clear otherwise—or the result will be a meaning one did not intend. If you always use the comma, you don't have to worry about it.
Here are two classic examples often cited in discussions of how the meaning can come out wrong when the comma isn't used:
(1) An author's book dedication.
With the comma: I dedicate this book to my parents, Ayn Rand, and God. Without the comma: I dedicate this book to my parents, Ayn Rand and God.
(2) Concerning an article about a male movie star:
With the comma: Among those interviewed were his ex-wives, Prince Harry, and Johnny Depp. Without the comma: Among those interviewed were his ex-wives, Prince Harry and Johnny Depp.
I agree with Parla (in #4) and I have a question for you about my context:
Yesterday I read a sentence and it goes like:
The hot pot in Chongqing is very hot, spicy and peppery, but it attracts many more people than the milder style in Guangdong.
I read many threads about this serial comma, and I found that AE speakers tend to use it to avoid misunderstanding even if the meaning is clear. While BE speakers don't do that quite often. Of course, a native speaker also said "BE speakers do that more frequently because they are influenced by AE speakers currently." Anyway, my question is: do I need to add a comma after "spicy"?
I don't think it's needed for two reasons:
1)If I don't add a comma, when I am saying this to someone, they might understand in this way "....is very hot: spicy and peppery", if they have never tried this kind of food, they will consider hot pot is hot and hot means "spicy and peppery". But hot means "high temperature" and "spicy" and "spicy", "peppery" means something else, so if I include "hot", the meaning is clearly not "spicy" but "high temperature". So when I say this to my listeners, they'll understand the hot pot has high temperature, spicy and peppery.
2)If I write this, I'll choose a "dash" or ":" if I want to say "hot" means "spicy" and "peppery". I am a fan of Scienticfic America and I see the editors there use dash to explain what they are about to say rather than a comma.