Unless your photographers tell you to be inspired by those awkward, uncomfortable looking mannequins in the Forever 21 windows, hold yourself confidently and high.  You'll look much taller and thinner if you keep your back straight and your shoulders back.  Whatever size you are, hold your stomach in as well if you want to look more toned. Photography that is more avant-garde (experimental and/or unusual) may shy away from this.  If you're modeling for a photo shoot that is about shunning preconceived concepts, then by all means try it.  Your photographer will probably want you in not-so-true-to-life poses. It's important to be aware of exactly how you're positioning your entire body.  Nonverbal communication is all you have to rely on in photos.  Whatever you do, you'll be sending a message.  As a model you'll need to look natural.  This is where you may need to practice.  A key point is to keep your arms and legs relaxed.  You don't keep them straight all the time in normal life, so don't do it in front of the camera. Keep in mind the effects of light on your body.  The more angles you create in your body position, the more shadows which will appear. You'll feel a lot more comfortable as a model if you build a rapport with your photographer or director.  It will make the experience a lot more enjoyable, give you the confidence to introduce your own ideas and ultimately help you with future modeling assignments. In addition to making that project more enjoyable, the staff will be more apt to like you.  The more they like you, the more they'll think of your name when future projects come up.  And, possibly, the more they'll recommend you to another company. Unless directed by the photographer to do otherwise, when standing, put the majority of your body weight on one foot only; this will make your body make a naturally gracious "S" shape. Regardless of your body shape, doing this will simulate more of an hourglass figure.  Popping your hip out gives you a curve in just the right place.  Think of modeling in...

How would you rephrase that briefly using Vietnamese?
Giữ tư thế tốt. Nghĩ về điều mà bạn đang làm. Trao đổi cùng những người quanh bạn. Giữ dáng hình chữ "S". Không để sát tay vào thân mình. Chỉ cho thấy một bên bàn tay. Luyện tập, luyện tập và luyện tập.