I want to get this out of the way first. Music clearance is a fluid process, highly dependent on negotiation and relationships. Very little of what I am about to tell you is true 100% of the time.
That said, I’ve worked on a wide range of projects and often come across misconceptions that are 95% false and detrimental to the creative process. A few come up so frequently that I’m convinced there is someone going around to film schools and production companies actively spreading the same incorrect information.
As a filmmaker, an educated approach to music clearance will produce results beyond ensuring you don’t inadvertently cripple your film with an improperly cleared song (which is of course very important). Demonstrating patience and understanding of the process will also give you a greater chance of obtaining your “dream” soundtrack…both in current and future projects.