According to WHO (the World Health Organization), it’s important to clean your hands frequently, make sure that your mouth, nose and chin are covered, and handle the mask by the strap that goes behind your ears. Below is their info graphic on what to do.
Some things you should NOT do are wear a mask that is too loose or use a mask that looks damaged, dirty or wet. Don’t share your mask or take it off when you are not within the acceptable social distance of other people. Below is the WHO’s info graphic on what not to do.