Want to know the basic rule or marketing and promoting your music?
Constantly ask, “What do they really want?” (with “they” being anyone you are trying to reach)
Think hard, and don't take this one lightly.
Thinking of everything from the other person's point of view is one of the best things you can do in life. If done right, it will elevate you into the clouds along with a few select immortal beings.
Every time you lift up the phone. Every time you write an email. Every time you send out a presskit.
Think why people in the music industry are REALLY working this job. Try to imagine them as just a well-meaning human being who is probably overworked, looking for a little happiness in the world, and likes music (or the music world itself) enough to do what they do, even though they could be doing something else.
Think what their email “IN” box must look like, and how it would be unwise for you to send them an email with the subject of “hey” followed by a 7-page email detailing your wishes for success.
Think what people are REALLY looking for when they go out to a club to hear music. For some people, it's just a way to be seen, to increase their popularity. For some, they're searching for some music that does something completely original and mind-blowing. Some are looking for total visual entertainment.
Nobody owes you their attention. Not your audience. Not a person you happened to call or email. Not even the music industry.
Let go of your ego entirely. Think of everything from their point of view. Be their dream come true. Do what they really want.
(This even goes down to the smallest levels: what kind of phone message you leave, what kind of cover letter you write in a package, what kind of subject header you put in your email.)
And maybe, just maybe, they'll be or do exactly what you want.