If it is for another person see the Metta Bhavana flowing from your heart to the top of his/her head. Focus there for more than a moment and let it flow down to the forehead of the other person and then to the eyes and keep flowing down slowly and with intention all the way down to the feet. Now see the entire person as beaming with loving kindness. You release the flow of the Metta Bhavana and the person continues to vibrate on his/her own at the frequency of loving kindness.
By forgiving each cell of your body, your being is free. Only by being loving and kind to yourself, you allowed the other person to experience loving kindness on their own. Now that you see them as perfect and pure then bring your attention back to yourself. Do not bring back the connection from the other person back to yourself. This way you set them free and you become free as well.
If you want to use loving kindness as a daily practice then after you become Metta Bhavana, see the feeling flow out of every pore of your skin to the entire room or space you are in. Then see it flow to the building, the streets, the city/village, the state, the nation, the continent, the entire planet, the entire solar system, the galaxy and eventually bring your attention back to yourself. You have loved and been kind to the world because you are loving and kind to yourself.
Initially it might take a bit longer but eventually you can bring it down to doing the entire meditation in just one minute. At times there is no one to do this exercise with, yet you can do it with yourself. After doing this for 21 times, that is how long it takes to create a habit, you can quickly do a loving kindness meditation for yourself in 15 seconds. Do it at least for 15 seconds every hour.
Take a moment to gather yourself with one long inhalation, hold the breath and then exhale it completely. Now that you are centered, focus your attention of each part of your body individually starting with you head and moving down till you reach your toes. See your entire body filled and flooded with loving kindness, take another deep long inhalation and an exhalation. You may breathe two more times deeply before you open your eyes.
Until late, love and peace,