A big part of any portrait is getting the subject to feel comfortable in front of the camera. Most people are understandably a little uncomfortable stepping in front of a stranger with a camera and letting them take pictures. It may sound a little backwards, but one of the ways I get people to look natural is by giving direction on how to pose or stand. I'm not a big proponent of canned poses that may look pleasing, but force people stand in a completely unnatural way. The posing guidance I give focuses on making people look their best while feeling natural. I find this often helps build trust with my subject. I let people know when they're tilting their head to one side (most people do), or have the light falling on them in an unflattering way. This lets them know I really have their interests in mind and I'm trying to work to make them look their best.
I write all that with the portraits belowbecause they were all so open to my direction. Their portraits were all going to end up on the same webpage, so while each portrait doesn't have to be exactly alike, we wanted them to be similar. The people pictured were all congressional interns, who had just arrived in DC. Many came from across the country and had never been in Washington before.