I don't believe the "Wish List" function within Student Center works - it's been around for at least a couple years, but it doesn't have functionality yet. Some alternatives for scheduling include using Schedulizer (
Cornell University - Schedulizer) OR the "Favorites" function in the course catalog (
Cornell University - Acalog ACMS?) along with the Course and Time Roster (
Cornell University Registrar: Course and Time Roster Fall 2012).
However, while those will help plan out the classes you take, they don't show availability, in which case you may need to check the classes in Student Center and make sure they're not full! (I know this may sound like a lot, but it's not too bad and you get used to it pretty quickly!)