A slight shift in weight or change in angle can make a big difference in the final portrait. Since many of the subjects we photograph aren't professional models, they look to us to help them pose.
I just read an article that covers the basic tips that every photographer should have in mind during a portrait session. In 7 Killer Portrait Tips by Dustin Olsen, he illustrates how to position the subject to render more flattering outcomes. It's a good read, and certainly a post you'll want to bookmark.
In this portrait that I captured of model Leah Gerber, she demonstrates a few of these basic reminders. She's angled her torso for a more pleasing body line, and the hands are partially hidden. Her chin is at a good angle. I've softened the light using photo umbrellas on light stand. The strobes themselves are simple Sunpak flashes with a connecting cord that I often use in the studio.
A final tip that I would add is, that once you've covered the basic elements in a portrait, take a few more minutes to play. Try a different angle, experiment with another lens, and change the composition. You have nothing to lose because you already have the "safe" portraits, but lots to gain if you find that magical pose.