When you find yourself in a crowd, on the subway, or sidewalk, practice giving complete strangers a shot of Metta, one phrase, like "May you be happy," and imagine them happy in your heart, then the next... If you don't like crowds, just send Metta to every one you encounter for the week. If you work remotely on a tropical island or something and don't see folks, pick up a news paper or your yearbook from Jr. High and just give Metta, generously to folks.