Learning proper singing technique is of course vital to your success as a performer. However, more important than this is sense of your core, and your empathy with others -- in short, your humanity. Without these traits, a performer cannot hold an audience's interest, let alone captivate an audience. How do you develop these traits?
Be a social creature. Mix with people and nature, and realize that you are a member of both groups. When constantly engaged in a dialogue with your fellow humans, you will recognize essence of a great singer; it is same as essence of a great human being.
To develop this recognition, simply meet and greet people with warmth every chance you get. Greeting audience members before or after a performance is a good start. There are opportunities throughout your off-stage life for you to do this, also. Consider that even though you may be in a checkout line in a supermarket, or eating a meal in a Chinese restaurant, you're still on stage and still performing. The personas we unconsciously don when we interact with external world can help us connect with others, or distance us from others. The choice is yours. Decide to connect, and you'll discover resources that penetrate your persona. These resources can only help your singing.
Recognize that you are your first audience, and critic. You may not be your best audience or critic, but you can develop greater objectivity about how you sound. First, identify what it is about your singing that you like. Are there particular songs, or songs by a particular composer that make you value your singing more? Conversely, are there songs you sing that make you cringe at sound of your voice? Write these distinctions down, and find patterns in them to help you discover what exactly it is you like best about your voice.
Take time to record your singing, and listen to it. Many singers can remember their surprise when they first heard their own voice on a recording device. This surprise comes from change in perspective from singer to listener, and due to physics involved in listening to yourself while singing.
A metaphor to illustrate this can be found in sun. The sun is obviously primary source of heat for all people on earth. Yet, different parts of earth experience different amounts of heat. Why? Because media that sun's heat is "communicated" through are different for those living near Equator, for example, and those closer to North or South poles. Among other factors, ground near Equator is a more directed and thus effective reflector of this heat than ground near Poles. For both voice and sun's heat, source is same, but perception of it differs, based on means of communication.
The key point to gather from this is following: perception others have of your singing is an invaluable source of feedback you can apply to improve your singing.
Love all creatures and savor nature. Everyone has their own distinctive key to their inner humanity. The path to discovering what interests and even captivates another is different for each person. That said, there are some things that make everyone respond with warmth. This warmth radiates through us when we perform. Pets, for example, can bring out everyone's friendliness and warmth. A pet -- whether a dog, cat, hamster or goldfish -- can stir feelings of compassion and devotion in you. When we feel these things, they manifest in our body, gestures and expressions. How could such feelings not draw an audience's interest when you manifest them in a performance?
During Second World War, when a young man, I had a dog named Jerry. He was my constant companion since I was about six years old. I cherished him as a playmate. I knew he loved me innately, yet I took his love for granted. A short while after being inducted into Air Force, I received a letter from my family. Jerry had stopped eating after I left home, and had died from hunger, pining for me. To this day, every performance I give has a bit of that pain I feel from Jerry's death. Never underestimate power and resonance of love, and how it can affect your performance, no matter source of that love.
The effects that other elements of Mother Nature have on us can also help us engage our audience's interest. For one thing, it's said that being near water is a boon to solving many problems. I can't explain this, but can testify to it a bit. Remember last time you were at beach? (When your enjoyment of it wasn't hindered by a horde of people.) Do you remember feelings of calm and release that you felt then? This is nature’s great gift. Remember that our bodies are composed mostly of water. It's as if bodies of water, when experienced in natural, open and peaceful settings, somehow transmit their life-sustaining qualities to us.
Rather than judge, listen. There's a saying that goes, "Happiness is that condition felt upon seeing misfortune of a friend." That's pretty gloomy, yet it holds true when we judge instead of listening. Is it possible to listen when we want to judge? Isn't it just human nature to judge?
Judging means more than gauging apparent degree of similarity a person has to us. A man may judge that someone else is like him. Yet, he may not like himself. A more focused definition of judging is needed. I believe what we usually refer to as judging in social interactions is actually condemning and finding fault. We seek weakness so we can disregard what others are saying. We do this so another's views of world won't upturn our apple carts. Our condemnation of others is an indicator of our propensity to condemn ourselves. We must be gentler with ourselves, before we even face other people. How does condemnation help anyone? There's such finality in condemnation.
How effective do you think you'll be as a performer if you look out upon audience and feel only anger or an inclination to find fault? Will it make you any more effective to turn this harsh perspective on yourself? No. Listening is key to replacing such a condemning point of view. Listening helps us raise our consciousness, and that's just another way of saying, "Learning what is objectively true."