Is there a rule for using commas with multiple adjectives?

Solution 1:

A string of adjectives without any commas does look rather awkward, but it will (just about) pass grammatical scrutiny, especially in creative writing. Whether a strict teacher will allow it is a very different question...

Examples:

He was a short, fat boy in his youth, but grew up to be a tall, thin man.

The thin little old woman scolded the big fat pig for eating a small, thin turnip on his own authority.

I don't know the 'rule' that applies (mainly because I do grammar by 'feel' rather than rule) but you can be guided by this extract:

"The rulebooks tell us to put commas between coordinate adjectives, but because it is not always easy to tell when adjectives are coordinate, we apply two simple tests to be sure: First, we try placing the word AND between the two adjectives. Second, we reverse them. If, in both instances, the resulting phrase still sounds appropriate, we are most likely dealing with coordinate adjectives and should use a comma between them."

Source:http://www.getitwriteonline.com/archive/042301comcoordadj.htm