Yesterday Noël posted this in comments, and made me laugh:
I'd love to see an article on how cranky, misanthropic introverts should handle learning to sell their work.
If that isn't the story of my professional career . . .
Here's the main thing: when I was a cranky, authority-hating teen who pretty much pissed off everyone including my schoolteachers -- publishing parodies of them in the underground school newspaper probably didn't help -- I learned a valuable trick. In person I was a disaster, and often landed in detention thanks to my lack of interpersonal skills. On paper, however, I could be anyone I wanted to be. I only had to invent a persona to do the talking for me.
This is not to say you have to lie about who you are, what you write and how you'd like to get it published. The content stays the same. It's all in how you deliver it.
Let's say I have a short story that I want John Smith at Fiction Magazine to consider for publication. I'm in a bad mood tonight, so I'm naturally inclined to write the sub like this:
Dear Mr. Smith,
Enclosed is my short story, Cranky and Introverted, for your consideration. It's the story of an author struggling so much to fit in with the publishing herd that she kidnaps an etiquette teacher. I'd appreciate a response within the sixty days as per your guidelines as I have other editors I'd like to query. Let me know if you have any questions.
No matter how well the story is written, this query letter will likely get it rejected. John Smith is going to interpret the tone of this letter, and the tone shrieks I've got a chip on my shoulder, this industry sucks, you've got sixty days and hey, don't waste my time. Why would he interpret it that way? Maybe John Smith's had a bad day, too. Maybe he expects the deference, or just doesn't want to deal with someone who would write a letter like this.
Now, the same letter, but with one of my personas writing it:
Dear Mr. Smith,
Enclosed please find my short story, Cranky and Introverted, for your consideration. It tells the tale of a writer in desperate need of professional polish, and the etiquette coach she kidnaps to help her shine. Thanks for this opportunity, and I look forward to hearing from you.
The letter sounds a bit more friendly and inviting now, right? That's because the persona writing it was Friendly and Inviting PBW, who likes editors and wants them to like her and hire her and send her lovely big checks, not the evil Screw the Industry and You Too Pal PBW, who is presently popping ibuprofen for the tension headache that appears to be drilling into the gray matter behind her right eye.
The only technical difference between the two letters is that in the first I hit him with a reminder of the sixty day turnaround and in the second I didn't. I try never to give an editor a deadline; it's presumptuous and always sounds a little obnoxious.
If you're not comfortable with creating and using a persona on paper, then I'd recommend simply being as polite and professional as possible. An editor or agent will likely respond more often to a serious, courteous pitch than one that burns off their nose hairs.
There is more to cover on this topic (like what to do when you have to actually meet John Smith in person) but as most of the job is on paper, this is about 95% of the battle.