Life is sales. From getting a date, to getting a job, it's all about how you present yourself and what you have to say. Remember, sex sells. I, in no way shape or form, am suggesting anything illegal or immoral. I just feel that you need the right tool for the right job.
Personality also goes a long way.
If you don't get a call back, call again. I have never gotten annoyed with anyone who has called me repeatedly. In fact, I booked a couple of bands because of their persistence. Of course, if the talent buyer isn't interested, and lets you know that, don't push it. If there is no interest, I suggest a periodic follow up call to see if things have changed such as format or even the person who books the bands.