I've noticed that it's relatively simple to be better overall at relationships (business or otherwise) by following these three things:
Listen. Make sure you spend lots of time figuring out what's going on around you before you make a decision on what to do or not do.
Smile. People love happy people, and you'd be surprised how far a genuine smile can go in a conversation.
Laugh. If you're not funny, get good at being funny. People don't want to hang out with people with no sense of humor.
I am in no way an expert at interpersonal skills, so this blog is as much to me as it is anyone else. Since everything in the music business hinges on how much fun you are to hang out with, this is a big priority to me and anyone else trying to develop their career. Good luck!