After each adjective or adverb in a series of two or more when not connected by conjunctions.
He was a tall, thin, dark man.
The rule holds when the last member of the series is preceded by a conjunction.
He was tall, thin, and dark.
The comma may be omitted when the words are combined into a single idea.
A still hot day.
An old black coat.
2.

After each pair in a series of pairs of words or phrases not connected by conjunctions.
Sink or swim, live or die, survive or perish, I give my hand and my heart to this vote.
Formerly the master printer, his journeymen, even his apprentices, all lived in the same house.
3.

To separate contrasted words.
We rule by love, not by force.
4.

Between two independent clauses connected by a conjunction.
The press was out of order, but we managed to start it.
5.

Before a conjunction when the word which preceded it is qualified by an expression which does not qualify the word which follows the conjunction.
He quickly looked up, and spoke.
6.