These are the four most common ways to use commas:
1. To list words:
We need cheese, bread, coffee and biscuits.
2. To distinguish a name from the rest of the sentence:
Tell me, Holly, why you were early today.
3. To enclose additional thoughts:
He was, without doubt, the worst boyfriend my daughter ever had.
4. To separate adjectives:
He owned an eclectic, colourful, interesting selection of books.
However, sometimes adjectives do not require commas. Have a look at these examples.
• Sarah's blue silk skirt.
If the adjectives are part of the same object (blue silk skirt) you don’t need commas.
• Sipho's beautiful, snobbish, dangerous girlfriend.
Where the adjectives are separate descriptions for an object / person (beautiful, snobbish, dangerous) you do need commas.
From The Plain Language Programme by Amanda Pattersonhttp://writerswrite.posterous.com/the-comma