Regarding where to place your hands the best options are these or the combination of them: Loosely by your side, on your hips, in your pockets or both hands crossed on your chest. One of my favorites poses (that can be easily used both on LinkedIn or in casual social media) is crossed arms. In that case, pull your shoulders back a little and keep stomach muscles in check. If you are not a model (in which case you don’t choose your outfit), avoid hats for they form shadows on your face. Professional cameras show every pore and if you don’t want to wear corrective makeup, try to have a great night of sleep before your session to avoid dark circles and bags under your eyes. Avoid food that makes you retain fluids, like those rich in salt. Pick up a color to contrast against the background (in studio or outdoors) - if you are wearing a dark suit, pick up a red tie. Solid colors are less distracting than patterns, and you want the attention to go to you. So, if you choose a tie with a pattern, make sure it’s a discreet one. If the photoshoot is informal, don’t stick with the basics, try sweaters or shirts with vibrant colors. Also prefer solid colors. Avoid white pants. If you are showing arms or chest, five to ten push-ups before starting the session will pop up muscles and bring color to your face. Face wise, practice your smile in front of the mirror. Make sure that you smile with your eyes too! Practice with your phone as much as you can. The more you do it, the more you'll know what works for you and the less shy and more confident you will become in front of the camera. More on the general tips.