In this video Deanna McBreaty explains and demonstrates the proper technique for Fondues.
Leading with the knee, fondu to 45 degrees to tendu close in fifth position. Your heels should always be more further than your toes. Your knee should always be back as your grow taller when you tendu.
When extend to the back, always lead with the knee. You want to always focus on keeping your upper body tall and extended. This will help with your presentation while dancing.