Be yourself. Walk with your head up having chin alined to the floor, back straight, and shoulders loose and back having chest pop, as this shows confidence (even if you're not). Be sure to be confident, happy, outgoing, and fun. It can be hard sometimes if you're shy, and trying to be more "out there". Try to observe how the other people around you talk, and interpret that into what you say. Adapt to different peoples' personalities, but still make your talking your own. And being crazy is alright every now and then too, as long as its funny, and not something that's stupid or will get you in trouble. Never let someone take your attitude down and disappoint you,it just makes you nervous.Ignore Gossips and Rumors about you and walk on like nothing ever happened.
With a guy: Flirt, but not to the point of suffocation; find little ways to be flirtatious, but if you don't feel the sparks flying back at you, then stop flirting. Little things like, whispering in his ear, and brushing up against him by accident are what can drive him wild.
Be kind to people; do them favors, help them when they need you, be polite, compliment them. You will be well liked, and known in a heartbeat! Don't suck up to people, be sarcastic sometimes.
Get in shape exercise and tone up your body. Find an exercise that works for you. You don't have to look anorexic to be in shape. Looking fit is more attractive than being too skinny. Remember, the people in magazines are not the real image of beauty and they are all air brushed. Do little things like integrate more fruits and vegetables into your diet. Eat all of the required amounts of fruit and/or vegetables for your age, and make sure to make an effort to work out at least a little bit. It gets old, but drink at least 6 glasses of water per day.
Wear stylish clothes, buying clothes that are in style is key. If your parents don't want to buy you clothes, save up money and go on a mini shopping spree for yourself. Go to stores you like and browse for items on sale; they can be just as good! Keep your own style, but try to follow what your peers are wearing also. Don't buy clothes that are too tight fitting, or too revealing. Make sure the clothes fit you. Show off your best assets and hide your flaws. Pick out bright, happy clothes with plenty of color from your closet. Wear denim miniskirts, shorts and low-rise jeans. As for your shoes, wear high-heels or shoes that make your legs look slim and long.