The prettiest, most flattering and soft light happens when the sun is closest to the horizon at sunrise or sunset. When shooting portraits, I liked to start shooting the last 2 hours before sunset. For the first hour the sun would be too harsh to face directly. During that hour I searched out even light, dappled shade, or used backlighting. Once the sun touched the horizon, we'd hit the magic hour or the golden hour which lasts about 30-45 minutes (or less) depending on weather conditions. This is the best time to shoot portraits in a natural setting using only natural light.
Examples of backlight, where the sun is behind the subject, and you expose for the subject.
Examples of silhouettes, where the sun is behind the subject, and you expose for the background. Hint: take the meter reading off the sky.
The only caveat is this light passes very quickly. It should also be noted that cameras with higher ISO capability and fast glass (lenses with wide open apertures) are pretty much necessary to shoot with natural light during this time without a tripod. Yes, it's a soft magic light but it's also a very weak light. The following three images are all examples of that moment when we had just enough light to face the sun, and you can see how perfect and even the light is in a natural setting.
The best quality natural light makes a huge difference with your photography. If you'd like to shoot portraits, try shooting during the magic hour. If you start shooting sooner than that - remember to seek out even light, dappled shade and use backlighting techniques until the sun reaches that magic hour.