I stumbled across this easy technique for finding good posture from Great Singers on the Art of Singing... Check it out!

1. Stand on the balls of your feet, heels just touching the floor.

2. Hold your arms at your side in a relaxed condition.

3. Move your arms forward until they form an angle of forty-five degrees with the body. Press the palms down until the chest is up comfortably.

4. Now let your arms drop back without letting your chest fall. Feel a sense of ease and freedom over the whole body. Breath naturally and deeply.

I tried this and I think it could be super helpful!!