I took a look at the job description and helped her tailor her résumé to that job, specifically. I made sure that the future boss would have all his job needs met, just from what she put on the résumé.
How did I do that? I taught our daughter how to think like the boss. For example, what would he want to see on the résumé first? What would strike him the best, that she was the most talented for the job, or had what he needed?
I also told her not to worry about the interview. He needed her more than she needed him, since it would just be for a summer job. Why did I do that? From years of being nervous in interviews. I found if you go into an interview knowing you're very valuable to the employer, he's going to see you as valuable. It's shown in nonverbal ways, to put him at ease that you know your skills and will give him a great product when you're done.
This theory is the same when applying it to pitches. The pitch could be what you write on the back cover, for the blurb, or what you say when you send a query letter or when you meet the agent or publisher for the first time. Know that you're the only one who can write that particular book with your voice, and it's unique enough that it'll sell.