A good, professionally query letter can mean the difference between an agent and an editor continuing to read material pasted below, requesting pages/chapters, or rejecting. As horrible and daunting as it can seem, you need to be able to write a good query letter. Snarky, clever, or rhetorical themes barely ever work so try to stay away from them. Be clear, concise, and professional. Here is what a good query should look like:
Dear Ms. McCorkle,
Due to your interest in steampunk/historical/paranormal (whatever genre your book is that I am interested in. Not all three, don't list all three. Pick the one your genre is that you know I'm looking for. Don't know, find out by reading my personal blog or profile page at City Owl), I'm confident you'll enjoy my steampunk (or whatever genre it is) novel, Such and Such (insert actual title). It is complete and polished at 90,000 words (read my word length preferences, know them, try to stay within them, understand that if you don't your book could be rejected based solely on that, or that I will ask you to either beef it up or cut it down).
Optional: Short one-sentence pitch goes here that states the problem, stakes, and solution that must be accomplished. Think of this as your quick one-liner to catch my attention. It can stretch into two sentences, but not over that. Think Twitter pitch length.
Paragraph One: with more detail hitting on the interesting or unique points of your novel that introduces us to the main characters and makes us want to know more about them.
Paragraph Two: This is the meat and potatoes, the why, the risks, the rewards.
Paragraph Three: Author bio. Keep it short and sweet and RELEVANT. Literary awards, memberships (RWA, SFWA, etc.), other published novels (self-published novels that sold over 5,000 copies warrants mentioning) and who they are published with, etc. Personal things that are relevant to the story may be included but aren't necessary. Education history isn't necessary and won't get you read any quicker.
Thank you for your time and consideration, I look forward to hearing from you.
Twitter / Facebook / Instagram
(Include links to your social media accounts, they can make a difference)
See how nice and short that is? It needs to fit on a single page. Concise is key! Last but most certainly not least: If the submission guidelines call for you to paste pages or material into the bottom of the email, don't forget to do so. It's frustrating to have to ask for material that wasn't included despite submission guidelines stating to do so. Doing your homework on submission guidelines, what a publisher/agent is looking for, and what they like is important on many levels.