This is a partial walkthrough that ends at Halloween, and gets all five girls to 60 relationship pointsas of version 0.7.9 , allowing you to choose who to focus on.
Things you should know:
The romance path isn't locked at Halloween, so make sure you don't accidentally push another girl too high after Halloween (easy to do with Rika, fx) before your chosen path is locked.
In order to complete a romance, you need to win all volleyball games. This means keeping average relationship of everyone but Emily above 65. So don't completely tank the girls you're not interested in, or you'll end up sad and alone.
New version (0.7.9.):