Just as you should not put commas around essential or restrictive information in a sentence, you must remember to put commas around information that is non-essential or nonrestrictive.
If the information is not essential to the meaning of the sentence, you need to be sure to set it off with commas. Here is an example of a sentence without proper commas around the nonrestrictive element:
The WiFi router which decides to stop working only during important meetings is blinking at me mockingly.
Here is the corrected version:
The WiFi router, which decides to stop working only during important meetings, is blinking at me mockingly.
If you have trouble deciding whether or not you need commas around “extra” information in your sentences, be sure to review the comma rules in the Punctuation area of the Excelsior OWL.