Another trick is humour. Everybody loves to laugh. So try to get the model to laugh. That will help loosen her up. And lastly, SHOW her what you want. Get up there on the cyc or on the seamless and show her where to put her legs or what expression you’d like her to give. If you feel awkward showing her yourself, gather your mood board or have some pictures on hand so you can show her, “This is what I’m looking for, smile (or frown or wink or snarl) like this girl”. Having a reference point will often set them on the right path.