1. Get informed: what shape is your body (pear, hourglass, apple, inverted triangle etc)? What undetone does your skin have (warm, cold, neutral)? Then see what shapes and colours compensate for your body shape and your skin undertone.
2. Start with standard elegant style (casual office style) and after a while adjust it to fit your personality
3. Buy a makeup case with lots of colours and see which ones match your face features
4. Choose some magazines or celebrities and look at photos, try to see what makes the outfits girly in your opinion
5. Always have a girly thing in your appearance : cute earrings, a nice ring, coloured nails, a glittery hairpin, a jumper with flowers on it etc
6. Last but not least, think of yourself as a girl, not a neutral human being