I love natural lighting. As I posted a while back! It's fun, it's free, and it's ever changing.
When using natural lighting, I focus on what I call The Three Ds: Diffusion, Direction, Discovery.
Diffusion
Bright direct sunlight can be harsh, both overexposing the image, and creating contrasting shadows. A way to combat this is to diffuse it. Overcast days are great for this - I used to think them dull, but now I see how useful they are. Shooting in the shade, say by a building or under trees, is another way to get around harsh sunlight. I'll post more about that next time. Inside, net curtains can act as diffusers too.
Example: First image is with the sun on him, the second was when a cloud covered the sun.
Direction
Direct the light just like you would with studio lights. Windows are ideal when taking photos indoors; sunsets give beautiful golden light from a very obvious direction; then you can position the sun behind your model to back light them, or place it at 45 degrees from the front to it's not directly in front of them.
Examples: First one is looking into a sunset over a river, the second uses the window to direct the light to the model.
Discovery
Discover what you can do with light and shadow, create halos, starbursts, bokeh... Experiment!
Example: I caught this bridesmaid in the sunbeam perfectly at a wedding. Yes, her eyes are darkened by shadows but the overall effect makes her glow, and stand out from the background.
