How do you know if a nice guy is just being nice or if he actually is interested in you?

If he is actually interested in you he will hang out with you. If he's just a nice guy he'll just be nice to you and talk to you and act friendly. It makes sense right? If he likes you he'll want to see you outside of school and band and stuff, if he's just a nice guy then he probably doesn't care that much whether you hang out.