Compare the two images of the same model taken a minute apart. Why does the one on the right seem so much stronger? It's a combination of the 3 steps below.
After selecting your overall light configuration (light system, light roles, modifiers, and configuration):
1. POSES AND ANGLES:
It starts with the model striking a pose (can be at the direction of the photographer or an idea the model has). I often keep idea galleries handy to help us consider various poses and especially options for angles, placement of the hands and head, etc.
In the image on the right, the model's head is slightly tilted and positioned a bit down resulting in a more attractive shot. Also, he is leaning slightly forward toward the camera and this is inviting the viewer to interact vs. if the model is standing back.
None of this is to say that all models need to do these precise movements -- rather, with this specific model at this camera angle, there's a strong difference among two options for positioning. There are many other possible options that could have resulted in a strong or weak shot.
I believe most models (and others) spend a great deal of time taking selfies. This is great when it comes to knowing how one appears on camera. Whether you use your webcam, phone camera, or simply spend a lot of time looking in the mirror, you can gain valuable insight into how angles impact your look. I want models to bring this awareness to the shoot and it is helpful to review some selfies that have strong impact and talk about the model's placement relative to the camera.
Also, it is critical for the model to have something in their mind that they want to convey vs. a blank look into space. I often ask the model, "what do you want to communicate in this image?". When they say, "I have no idea", it often matches with a blank look. I discuss the idea of slightly squinching the eyes to give a more intense gaze. We discuss smiling vs. a more typical "model look" too. When the model does have an idea in their mind, it is often a seductive, confident, or successful image that they wish to convey. The angle can change not only based on how the model moves, but also where the camera is positioned.
This step is owned by both the photographer and the model. While some models prefer to be directed, it is important for a successful model to partly own posing. They should study images they like and then try many selfies to see how they capture. A great model brings ideas about posing and is not afraid of trying different angles. Two feet planted squarely on the floor is not usually the most interesting pose. Triangles can be a nice element (arms, torso, etc.)
You can either move the model to impact how shadows fall on the model's face and clothing or bare skin and/or you can move the lights and keep the model in a single place. The left image has less light falling on the model's face, resulting in a very narrow looking face.
I love using some shadows and having light positioned at an angle to the model (not straight on), brings out texture and adds "drama" to the image. For example, if you wanted to highlight a model's muscles in their chest, a side light will create some dark areas (contrast) that bring out the definition. A light source from the side can produce very dramatic shadows. In this case, you may have a fill light (or reflector) on the other side to avoid a completely black shadow without any details. If you light straight on, muscles and textures of clothing will not be as visible.
In addition to the placement of the lights relative to the model and background, you can change which light modifiers are used. These can include a beauty dish, grid soft box, or a large octabox -- and others. You can add color gels too. All of these options impact the quality of the light reaching the model.
The most basic choice when considering the quality of the light is: soft light vs. a more direct hard light that creates more shadows.
I often will ask the model to hold a pose while I fine tune the lights and exposure. We may also need to re-take a shot due to eyes closed or facial expressions that are off. Once we get the shot, then he can try another pose and I re-check the light falling on his face and body.
An experienced model will think about light sources (including key, fill and hair lights) and have a sense of where to stand relative to the lights. The right shot above includes a hair light which helps offset the model's dark hair from the black background.
Some models want to move a lot during a shoot. I find it difficult to adjust the lights and maintain perfect focus when the model is moving too much. At the same time, some small movement can appear more natural and less stilted.
3. CAMERA SETTINGS: EXPOSURE, COMPOSITION AND FOCUS
The last step is all on the photographer to deal with. Once your model's angle/pose and lighting looks good, you want to think about how you compose the shot.
Additionally, you want to review your exposure and relative amount of each light source. Are the hair or kicker light too strong or weak relative to the key light? If so, you want to adjust one or the other. It's all about "relative" light values that create your shadows and highlights. If you blow out the highlights or have major shadows where you want some detail, there may be nothing you can do in editing to recover these unrecorded details.
While you can crop later, it is helpful to have an idea of how you want to place the model in the view. I always check the focus to be sure the eyes are super sharp. Consider what focal length is appropriate for your shot. Often, I use a 70mm to 200mm lens when shooting portraiture in the studio.
THE ORDER: While you can certainly change the order of the above items, I find it helpful to pose the model in the general spot first, and then adjust lighting. Often, we're taught about lighting as the first thing you set-up, and then the model is placed in position. In reality, it is a combination of both -- you start with a general lighting configuration for each set, and tweak the exact positioning as the model get's into their space.
That's it. A confident model, well placed relative to LIGHTING in an attractive POSE and proper CAMERA SETTINGS = a great shot.