We photographers always love the latest pieces of studio gear to elevate our photography skills to a higher level, but we tend to forget that the most important studio equipment that we have is God-given: our eyes. I love to do outdoor portraiture using daylight. In order to create natural looking portraits, we have to learn how to "see the light". By knowing so, we will be able to understand natural light much better and know exactly what to add or subtract when we have modifiers next time.
Although cloudy days are great for diffused light, sunny days are much better in my opinion because light can reflect off a variety of surfaces for the extra 'punch'. One tactic of utilising daylight is using natural reflectors which are almost anything, really: tree foliage, signs, sidewalks, and buildings. Just be aware of the opportunities which are present, and use them to your advantage.
I had no trouble adding light to the shadow areas, because light was reflecting everywhere from the white sculptures and the concrete sidewalk. Just be aware of using light from below; if its too strong, it creates a "ghoul lighting effect" which isn't too pleasing.
Although this image uses natural lighting, I did use a hint of direct fill flash. Why is that, you may ask?
So what are you waiting for? Get off your lazy bums, take that beautiful model friend of yours out on a sunny day, and start shooting!