Commas with Some Adjectives

Use commas to link coordinate adjectives, as shown in these examples:

Arnie is an intelligent, creative, helpful boss.
Susan is a compassionate, caring person.

Commas actually stand for the word and between coordinate adjectives. Consequently, your sentence should sound correct if you read and between each of the adjectives. However, do not use commas with non-coordinate adjectives. Consider this example:

I like to sail on an old wooden boat.

In the above example, the adjectives old and wooden cannot be rearranged without changing the meaning, as shown here:

I like to sail on a wooden old boat.

When adjectives cannot be rearranged, they are non-coordinate and should not be separated by commas.

Which sentence is correct? They made arrangements through a reputable, online, travel service. Our tour guide was a knowledgeable, articulate, and humorous gentleman.