The models pose
The model's pose is crucial to the success of the photo. Often photographers get carried away with the technical aspects of the shoot, such as ensuring the exposure is perfect, making sure the model remains in focus, the framing of the shoot, and controlling the lighting set up, that the actual fine tuning of the model's pose is often overlooked. Then, when you look at the pictures after the shoot, and your photos are technically brilliant, a photo can be ruined by an unnatural pose, or something as simple as a clenched fist, a creased shirt, out of place hair, a uncomfortable head position, or well… you get the idea. It is therefore crucial that you not only ensure the technical aspects are perfect, but at the same time you are directing the model, and creating a natural comfortable pose.
When a model is uncomfortable it most certainly shows in the pictures, therefore take the time to ensure your model is comfortable, and at ease. Discuss the shoot with your model before hand, to get a common understanding of the shoot. Some models prefer moving around by themselves, while you shoot away, occasionally adjusting a pose you like. Whereas other models prefer you to direct them completely, where you will need to tell or show them exactly what you have in mind. Either way, for the best possible photos, make sure that you have discussed this and have a clear understanding.
It is said that the head and the hands are the most noticeable in the photo. So make sure that the head has a natural or comfortable tilt in the photo. Also make sure that the hands are either fully in the frame or out completely, a half cropped hand really does not work.
An easy way to break the ice, and make the model more comfortable in the photos, is to bring some props along. This will give the model a character to work with and should loosen up the process. Examples are a pair of sunglasses, a chair, a hat, etc.
The best way to have a shoot is to just have fun, if the model is enjoying the shoot, and you mastered all the technicalities mentioned above, the photos are bound to be successful!