The way you stand when you sing has a big effect on how you sound. Good posture helps air to rush into the chest, and creates freedom in the lower abdomen for the singer to control the breath support. Stand tall & straight, with feet slightly apart, and think of your spine lengthening and your back widening. Hold the chest high when you breath in and allow it to collapse as you sing. This is useful initially to encourage internal movement of breath. Once you have strong breath support, you won't need to exaggerate movements to quite this extent. When you sing you should imagine you are on stage singing out towards the back third of the hall. This encourages good posture, and will look natural & alert on stage - energetic, involved in the performance. When you perform, you must periodically address your audience in a directional sense, so that they feel you are singing to them, & so they feel involved in your performance. If audiences feel you are merely singing for your own entertainment, they may appreciate the skill, but will not become emotionally involved.