This kind of confidence usually takes years to develop. Before I ever saw her photographs, I knew how they would look. They were great. She had a good sense of composition, and by getting as close to her subjects as she did, her photographs looked like they had been taken by a pro. There was actually very little difference between her photographs of the Faire and mine.
Many factors go into making a great photograph and great photographer.
You must have confidence in yourself and your equipment, know composition and color, understand your film and the development process and much more. But if you get close to your subject you will be astonished at how well your work photographs will turn out. If you think your subject might object, then ask their permission. Most people don't mind being photographed, especially at public events. Very few people have ever objected to me photographing them.