My friends and I play a mix of public and private golf. Each time we want to book a tee time or plan to golf at one of their clubs, it is a challenge coordinating everyone's availability. Furthermore, people will commit to playing without realizing they have some prior commitment they forgot about. How do you ensure you fill your foursome prior to booking a time or filling out a tee time you already reserved? Are there any apps out there that help make this easier?