No really, having to do portraits of people that you don’t know is very unnerving. Sure you can pose them however you like, but then you end up with a stiff look in usually an awkward position. Sure it looks easy enough for the photographer, but he is not the one who has to hold that pose until the strobes fire. I look at catalogs of studio supplies and the “example pictures” that they show. Complexly designed scenic backgrounds, props, etc… and the person looks that they are acting or standing in a way that they would probably not do in real day to day life.
I, personally, as a fan of the simple backgrounds and setups. better yet, I rather take the whole shoot outdoors (if the weather is descent). My best portraits so far in my portfolio are of people that I knew well.

David & Amanda. Good Friends (my first wedding too)
Taking pictures of friends and family tends to look the most natural. They know the photographer, the environment and sometimes even what to expect. Even if the idea sounds crazy. See examples below.

From front to back (Luke, Matt, Roy)
My Favorite part of this shot is that every facial expression is a fairly accurate description of each of their personalities. The Artist, the athlete, and the musician.
Lastly, even with a fairly unknown subject, I try to really get to know them, what they are into. With high school seniors, it’s where they are going to college, what are they going to major in, their sports interest, their senior activities etc… Usually we start getting crazy and creative around the last half an hour or so of a shoot. I open the floor of their ideas and suggestions, or an image will flash in my head about a pose. In some cases I can “see” the shot before taking it then I have to make it work.

Kevin (Senior, guitar player, musician)
All 7 Seniors that I did shoots for this year chose very non traditional portraits for their yearbooks. I don’t see myself as a “traditional” photographer, but I’m not way out there either. Creative, i guess, is my happy medium.