1. BCC Is Your Friend
When you send an email to a group of people, use the BCC (blind carbon copy) field. If you don't, everyone who is copied on your email list can grab the email addresses of everyone else - and not everyone is going to be cool with that. Using BCC says, hey, I appreciate having this line of contact for you, and I respect your right to decide who does and doesn't have this address. This is true of both industry email lists and fan email lists.
Of course, accidents happen. If you accidentally CC rather than BCC your email list, apologize. It still might not make you the most popular kid for a little while, but at least you have acknowledged that you understand that you have compromised the privacy of the people on your list.
You're waiting for some feedback on your song/business prop/etc. And you're waiting. And you're waiting. And it's just not coming.
Frustrating? Oh, absolutely. But there is a line between following up territory and restraining order territory. Don't cross it. Unless the entire world will collapse if you don't get an answer on something by 6 PM, if you're calling or emailing multiple times per day, you're probably going overboard. Likewise, don't track down home numbers, etc, and try to catch people out that way. If you make multiple follow-ups, a simple, "I know you're busy, but..." and a "please let me know if you need more info" make gentle reminders that you're waiting for news. Stay polite, annoying as it may be.
The first time you make contact with someone, give yourself a proper introduction. Don't assume they know who you are, and don't do things like (one of my personal faves) send an email that simply says something like, "let's work!"
Of course, don't start at birth, either -. "Hi, I'm so and so from such and such" plus a few details and maybe a website link work fine. Then, explain why you're reaching out, be it booking a show, soliciting advice or just because you like what they're doing and wanted to open a line of communicaton. If you're hoping to meet up or have a phone call to discuss something, say so and suggest a few times. Be clear and concise - you're more likely to get a response if people can actually understand what you're after.
4. Keep Your Appointments (And Buy The Coffee)
If you make an appointment with someone, keep it or reschedule it. Bonus points for being on time or calling if you are going to be late. It is just good manners, period. Plus, not showing up for a meeting makes you look irresponsible, unreliable and scatty.
Likewise, if you request a meeting with someone to ask for advice or pitch something to them, consider springing for their coffee/drink/meal if at all possible. It is a gracious thank-you for their time. Of course, money can get pretty tight in the music industry, but if you can do it - go for it.
The music industry is a very small place. You may have the goods on a lot of music business deals gone wrong, not to mention the personal goods on what so and so did on tour or why so and so got booted from the band. Tempting as it may be to blab - zip it. This is doubly true of your own deals gone wrong. You may feel incredibly slighted by your band break-up or management collapse, but take the high road when pressed for details.
Two good reasons to button your lips? Well, one: gossip is a two way street - you probably have a few stories of your own you'd appreciate someone keeping close. Two: being a big mouth says, "if our working relationship doesn't work out, I will violate your trust, too." Doesn't exactly instill confidence.