Stand comfortably upright with your ribcage lifted allowing the maximum expansion of your diaphragm. Hold your arms at your sides or slightly in front of your body, feet shoulder width apart.
Hold your head straight, chin up and face forward to keep from restricting your airflow.
Breathe deeply from your diaphragm (below your ribcage). If your shoulders lift when you take a breath, you are breathing shallowly from your lungs. Hold your hands on your waist to make sure the ribcage (and not your chest) expands as you breathe.
Raise your arms and smile if your pitch flattens. For high notes, raise your face slightly to open the larynx. Drop your jaw (but keep your chin up) if your voice goes sharp (too high).
Relax. Sway with the rhythm. Tension constricts the throat and deforms vocal tone. Control your tone, power (resonance) and pitch using the muscles of your diaphragm. As you grow stronger, you can safely try screams or throaty hoarseness with proper singing technique.
Practice daily. If these techniques (or the flu or overusing your voice) make your vocal folds swell, use a humidifier to keep your throat moist and split them in two sessions.