To not be shy around girls you need to increase your level of confidence. Practice having something to say or ask them. It can be about school, friends, music or just something going on at the time. Smile, and look them in the eyes. They won’t know if you are scared inside, only you will. Do this a few times and it will be easier. Always try smiling at them first to see if they will be receptive to you. Remember, the world won’t end if you mess up, just laugh and keep going.