Sometimes it isn't what you do that costs you the job, it's what you fail to do. Unfortunately, there are probably a thousand or more little things you can do to get turned down so I'm working on highlighting some of the bigger issues for you so you know what to avoid. The first part covered incomplete emails that lack key personal and contact information. I'd daresay many of you are guilty, so check that post out here for some tips.
Once you've sent a great email there's still something else you need to be sure to do: follow up. This means checking back in whether or not you get a response or not. People are busy and emails get lost in the shuffle so make sure you reply after a few weeks to see how things are going. Bonus points if you actually pick up a phone and try calling. Sure, it's possible a lack of response means rejections but it may also just mean the person hasn't had a chance to look at your message yet.
The imporant of follow up isn't limited to initial contact thought. It also means generally responding promptly (even if you are no longer interested.) For instance, if you write to someone in the music industry asking for some advice or help on something and they take the time to reply to you, respond and thank them. If you applied for a job and get a response but are no longer interested, again reply, explain it and say thank you. Ok, so that won't help you get a job immediately but the industry is extremely small and you don't want to come across as rude or ungrateful. As I said, emails can get lost in the shuffle of daily life so it's certainly reasonable that you might have missed reading the email, but still it's usually better to respond a bit late and say thank you than to continue to ignore it. This also means continuing to follow up throughout the application process. After an interview, send a note. Ultimately, your job search isn't just about putting your qualification on paper and hoping someone is impressed, it, like most things in the music business, is about people and relationships. So, showing that you are attentive enough to details and able to appreciate people's time and efforts can go a long way to making you look professional and be one more thing in your favor when the HR department is deciding whether to trash your resume or move it to the pile for consideration.