Review basic technique. Pout your lips and blow as if you were blowing out a birthday candle. Place the tip of your tongue behind your bottom teeth and blow lightly. Practice until you hear a whistling sound.
Keep your lips moist. The best whistling sounds are made by smooth lips. Children will learn how to whistle easier than adults because their lips are naturally smooth and moist. Adults need to keep well-hydrated to avoid cracked or peeling lips that will interfere with a clear whistle sound. Use lip balm to moisten lips, if necessary.
Practice away from people. To master the art of whistling, you will have to practice a lot. You may have to practice for weeks or months before you become a master whistler, so be kind to others by practicing in solitude until you are happy with your results.
Practice in front of people. Whistling better requires confidence. Build confidence by whistling in front of others once you are happy with your technique.