When you have to collect Fairy Wings as part of your homework assignment for Professor Snape you will get the chance to go to Hogsmeade (The Woods outside Hogwarts). When the fairies come out, use Hermione and cast the Flipendo spell (KNOCKBACK JINX) and if you hit them then they will fall to the floor. You then have to use the Glacius spell and freeze the fairies, then walk over and pick them up.