Improve your posture. Stand up straight, pull your shoulders back, and suck your stomach in and up, like you’re trying to zip up a tight pair of jeans. If you really want to suck in your stomach, you have to make sure to do it subtly, so that people don't notice your ribs poking out in the photo. It's better to look a little heavier than you want in a photo than for someone to say, "She sucked in!" Just maintaining good posture can go a long way in making you look tall, more confident, and more thin.
