1.Be Loving and Caring to others. Instead of fretting about your appearance all the time, try to focus on others. Show your family and friends that you love them through kind gestures. If someone appears lonely or upset don't just ignore them, go and make them feel welcome or soothe their troubles; people will learn that your a lovely person and will not only feel comfortable around you but you'll also appear twice as beautiful in their eyes.
2.Be Yourself. Yeah I'm sure you've been told this so many times. May be it was first advised to you by a parent on your first day of school, but do we really understand how important this is? So many people try to mould themselves to fit other people's ideals, but why change yourself? If they can't love and accept you for who you really are, then they aren't worth being around anyway! Surround yourself with people who love you for you, not the fictional character you create just to 'fit in'.
3.Focus on your Assets not your Flaws. Look in the mirror and focus on the things which you love about yourself. Its human nature to 'see the glass as half empty' and want the things we haven't got when everyone has got something which others envy, including you! We're all human and we all have flaws but we need to embrace ourselves and love the assets we've been blessed with. Be positive!
Just keep on smiling :)