All of the Good Luck Charms like the Shooting estrela are given out at random. You'll just have to stay active on the 'Pop and eventually you'll earn it.
Caps are given on certain special days of the ano ie the coração one on Valentines dia or how many days consecutively you visit Fanpop.The rest are pretty much given at aleatório so just sit back,keep visiting and you'll get your Shooting estrela soon enough.I think this earns me at least one prop! ;D