Many ways exist to flirt with a middle-school girl, whom should be between the ages of 11-14. Girls of this age group like to talk a lot about their favourite movies, music and of course, their favourite boys. It can be very intimidating for a middle-school boy to approach a middle-school girl, especially if she is hanging out with several other girls. Flirt with them in age-appropriate ways and only if you are in this age-group yourself!
Try to be a friend, and not a boyfriend in the beginning. Sit with a girl at lunchtime, so that you can get to know her. Ask her questions about what music she likes, and allow her to ask you the same questions. Offer to help her with her homework, or perhaps ask her to help you with yours. Listen when she needs someone to talk to, and show her how nice a person you are.
Approach a girl and compliment her, but don't overwhelm her with dozens of compliments. Tell her how nice her outfit is, or tell her that you like her book-bag. Notice something different about her, such as her hair, and compliment that.
Play with her pigtails or ponytail, or simply rub her head playfully. Gently nudge your shoe with her shoe under a lunch table or school desk. Offer to hold her hand during a school-movie or during a pep rally.
Buy her something small and inexpensive, but something that is special. If she likes ladybirds and earrings, buy her a pair of ladybug earrings. If she likes music, make her a mixed CD of her favourite artists. Show her that you like her by giving a personalised gift.