I agree posing can be hard, particular once you are in the middle of it. I try for natural ways in which people stand or sit and then just make minor adjustments to start. That often leads into me having more ideas. I also find that movement seems to make for a natural look. It's fun to work with someone who has done a bit of modeling before and watch out they move and interact with the camera. So much more fun than static poses for me.
working with someone who is comfortable in front of the camera and knows what is going on is like a cheat code :D
movement helps go get it look more natural.