1. When you purchase your mussels, make sure to immediately unwrap them at home so they can breathe.
Discard any mussel that is chipped, broken, or damaged in any way. Also, discard any mussel that is open. The mussels should be tightly closed and stored in a cool area where they can breathe.
2. Just before cooking, soak your mussels in fresh water for about 20 minutes. As the mussels breathe, they filter water and expel sand. After about 20 minutes, the mussels will have less salt and sand stored inside their shells.
3. Most mussels have what is commonly called a "beard," also known as byssal threads. The beard is made of many fibers which emerge from the mussel's shell.
4. To remove the beard, hold the mussel in one hand, cover the other hand with a dry towel, and grasp the beard; give it a sharp yank toward the hinge end of the mussel. This method will not kill the mussel. If you were to pull the beard out towards the opening end of the mussel you can tear the mussel, killing it. Discard the byssal threads.
5. Remove the mussels from the water. Don't pour the mussels and water into a strainer because the sand has sunk to the bottom of the bowl; you'd end up pouring the sand back on top of the mussels. Put the mussels in another bowl of clean, cold water
6. Use a firm brush to brush off any additional sand, barnacles, or other oceanic attachments. Rinse the mussels under cool tap water, and set aside. Dry with a towel before cooking.