Stand or sit and keep your back straight to open up your throat so the air passes more easily through your vocal cords. Keep the muscles around your lips loose and then close your mouth.
Put both index fingers below your cheekbones right next to the corners of your mouth and then take a deep inward breath.
Exhale slowly and push the air through your mouth. This will create an air pocket, or bubble, and allow you to easily roll your lips as you begin to sing.
Sing scales while pushing air through your lips. The quick pushing of air bubbles through your lips will cause them to vibrate with the fast opening and closing of your lips.
Keep your neck and throat muscles relaxed as you sing scales and patterns in your range to complete the lip rolling vocal exercise. Don't strain at the upward end of your range or you can do more damage than good for your voice.
Practice this exercise daily as a warm up to strengthen and relax your vocal cords and mouth. As you master the lip rolling exercise, your head voice will begin to sound more like your chest voice and it can help you to get over your bridge without breaking.