Play with makeup. Try different colors, styles and see what suits you best. If you already wear makeup try cut it down to a minimum. Buy some new clothes that express your individuality and wear those. Try add feminine qualities to yourself, like wearing a dress of nice skirt. Colours too. If you want to look sexy and bold, wear red on one day. If you want to look vulnerable and cute, wear a peachy pink. Wear colors that suit your skin tone and clothes that accentuate your nice features.
Style your hair too. If its straight, try a waves, or curls. Vice versa. Start smiling more and looking at things from a positive perspective and you're good to go!