When I attended my first SCBWI conference, I heard many editors speak. Including the guy who…um…edited Harry Potter. He described how he preferred to be contacted: query letter only – if he liked the pitch, he'd request the manuscript.
I returned home and wrote my first query letter. It was the first piece of mail I had sent to anyone in the publishing industry. I thought my letter was decent (I had listened to what the editor was asking for. I'd looked up some sample query letters on the Internet. I tried not to make any obvious wrong moves.) But I honestly had no hope; I had heard over and over again how hard it was to get a yes from anyone.
Two weeks later, I received a yes!
I've written many more query letters since then, and the response has always been good (my request rate is somewhere in the neighborhood of 80-85%.) That is not to say you have to do things the way everyone else does. But it doesn't hurt to be professional, to pay attention to the editors' and agents' preferences, and write a great pitch!
If you're taking the crash course, return to [step seven->step seven – send out your work].