Summarize:

Since incorrect turnout can damage muscles and lead to knee problems, it's important that you work on your turnout with a professional ballet dancer. Try to find a pre-professional ballet school that is associated with a professional ballet company. This way, an instructor can give you individual attention, helping you achieve the perfect turnout. Since the muscles of young ballet dancers are still developing, it's easier to improve flexibility when you're young (before age 12). Before you turnout, stand in front of a mirror with your feet touching and facing forward in a parallel position. Keep your muscles flexible and make sure your tailbone is pointed down, not pushed out and back. Stand firmly on your feet. If you're too tense when you begin to turnout, you're more likely to cause muscle strain and injury. Spend at least 10 minutes stretching your leg and hip muscles before dancing. Once you're in the correct position, lift your toes up and away from each other (in opposite 90 degree angles). It is critical that you do not simply twist your feet away by using your knees and lower legs. Instead, shift your weight to your hips so that your feet naturally move apart. Make sure you're not putting all your weight on your big toes, instead of distributing it throughout your feet.  The ideal turnout is 180 degrees. Don't worry if you can't turnout that much. Stretching can improve your flexibility by a few degrees. Good turnout also means that you're honest about what your natural turnout is and don't try to force it.  Make sure your weight is evenly distributed throughout your foot. Poor turnout puts strain on just your big toes and rolls your feet in. Instead, your feet should be level with the ground. While it may seem easy to use your knees in order to spread your feet farther apart, do not do it. This will strain your knees and legs. Research shows that this causes poor alignment and can lead to injury. Turnout should feel like a natural stance. You shouldn't feel any strain in holding it while in any position. If you continue to practice poor turnout, you'll begin to feel knee pain and muscle ache. It's easiest to force your feet when you're in the 5th position. But, you should always be on guard against improperly rotating out your feet.
Find a professional. Get ready to turnout. Get in position. Avoid forcing your turnout.