Sometimes pro models get intimidated in front of the camera, so we've gotta expect it from our non pro models, right?
We need to help them out to feel more comfortable.,it's our job after all. Props now become our best friend!
Give the subject something to play with to put them at ease. If it's a head shot then the prop can be help in their lap and doesn't appear in the photo! Alternatively, make it part of the photo! Perfect.