Do you put a comma after the second word in sequence of 3?

You're asking about the Oxford comma, which is the comma that goes before the conjunction "and" in a list of three or more items.

There's no hard and fast rule about the Oxford comma.

* Some style guides require it: The Associated Press (AP) style guide, for example, mandates the Oxford comma.

* Other style guides don't: The Chicago Manual of Style generally prefers it but allows it to be omitted in certain cases.

Here are the two ways to write the list:

With the Oxford comma:

* My favorite things are chocolate, peanut butter, and ice cream.

Without the Oxford comma:

* My favorite things are chocolate, peanut butter and ice cream.

The key is to be consistent within your own writing. Choose one style and stick with it.

Here's a tip: The Oxford comma can help prevent ambiguity, especially in certain cases:

* "I invited my mother, my father, and my aunt to the party." This clearly shows three guests.

* "I invited my mother, my father and my aunt to the party." This could be interpreted as two guests (a mother and a father who are also an aunt).

Ultimately, it's up to you!