Joash, portraiture, while different in it's approach, isn't all that different from any other form of photography when it comes to execution. Just as the sun lights a landscape, you light your subject in very much the same way, and everything else boils down to design elements, principles, and if you're lucky, a special moment.
For instance, these first two shots were taken around the same time in pretty much the same place. Basically I'll I did was turn 180 degrees facing north for one shot then south for the next with the sun coming from the east. See how I used the warm soft side light in exactly the same way.
If the light is difficult, use it to your advantage, play with your exposure and allow it to give form to your subjects. Then you just compose accordingly and wait for a moment or look.
If it's bright outside, shoot in the shade, just be mindful to watch the subtleties of light in the shade. Ask yourself what's it doing, and where is it coming from. Then again, just compose accordingly,wait for something to happen, then shoot.