for opening phrases, conjunctive verbs, etc.

1) Introductory or opening phrases.
In general, sixty-eight is quite old to run a marathon.
On the whole, snakes only attack when riled.

2) Conjunctive verbs.
Unfortunately, the bear was already in a bad mood
and, furthermore, pink wasn't its colour.

3) Following for example, that is, etc
You should use commas, for example, around 'for example'.
There are some exceptions: namely, when using abbreviations.

where a pause is required

1) To make the reading more natural.
Whatever happens, don't panic.

2) To avoid confusion.
To Margaret, Jenny left her favourite book.

in address or quotation

1) When addressing someone by name.
So, Murray, I'm sending you to Outer Mongolia.

2) When quoting direct speech.
And then the boss said, "I'm sending you to Outer Mongolia."

to indicate the omission of a word or phrase

Use too much sugar and the mixture will be sweet, [use] too little and it will be sour.

Continued from Comma (page 1)