So how important is it—really—to know how to pose? Well, considering it's your only job in front of the camera, it's pretty damn important.
So what makes a good pose? Is it straight on? A Slight tilt? A 3/4 turn? It all depends on what look you're going for. Most photographers are looking for a pose that has impact and drama.
One of the most important poses you can master is something I call the “S” pose, which is exactly what it means. The model should try and emulate an S by moving her legs, hips, chest, neck, and head into the perfect S form. If a model gets this pose down, there is no stopping her.
Next to the "S" pose, a critical question of importance is “What should I do with my hands?” The hands can get to be awkward in a photo shoot. (See Practice in front of a mirror)
My first advice would be to always make them relaxed and uniform, never all cringed up. What to do with your hands is never easy and will take some time, so keep at it.
Hanging gently from your bikini bottom or gently through your hair is a good start. Some other tips are: try not to show your elbows straight on to the camera.
If you have a very round face, try and give 3/4 of your face to the camera by tilting your head. Same if you're heavy set; just moving your whole body to a 3/4 angle can do wonders to make you look slimmer.
Then, the model mantra: “Gut in, boobs out.” Never be afraid to exaggerate this as much as possible. It will always make a better picture. Never be afraid to take chances with your poses; the more extreme or crazy the pose is, the better it usually is.
Lastly, the importance of negative space, which is the space you create around your body. So instead of thinking about the pose you create yourself, think about the negative space you are creating around you while you are striking that pose. Of course, this has more to do with a designing element rather than a posing element.
In a way, your photograph is actually a piece of art with lines and empty spaces. If you come at it from this direction, which I hope you understand, you can really create something great.