So you wrote the next great novel. You are certain it is perfect. Random people you barely know have done reviews to say they love it and you even have a friend who does copy-editing who went over the whole thing for you. It is the absolute best you can do right now. So having poured your soul into a seemingly endless series of pages, you only have one more step to get the ball rolling. You have to convince a jaded editor or swamped agent that it is worth reading the very first page of.
More accurately, you have to convince them to read more than the first sentence of your query letter. Sounds easy right? Picture yourself in their place. Dozens or possibly hundreds of queries arrive each day. You are taking care of any number of other duties and have a window of time set aside for finding gems in the rough. If you casually read over each item in the slush pile, you are never going to finish in the time you have. Worse, you will waste a lot of time on queries from those who really don’t have something you can use or fitting your needs.
Unfair to the people sending the queries? Sure, but it isn’t the fault of the agent or editor. They have limited time and need to thin the crowd somehow. Maybe your first sentence is so bad it puts them off from reading more. Maybe something deeper in shows a lack of focus. Is that lack of focus something existing in the book itself? Maybe, maybe not, but that is all they have to go with so far.
My own suggestion, look to the pros. Of course there are a number of books on this matter and each gives its own insights. Realize that every agent and editor will be wanting something a little different or find different things catch their attention. After taking that into account, a great resource I have found is called Query Shark. It is cutting and harsh, but helpful as well. Janet Reid takes time out of her own schedule to review the queries of people who send them in and then rips them apart. She levels the gun and gives both barrels, pointing out every possible mistake you can make. As of this posting, she has done 248 of these, including the revisions. Each one offers insights into what to do and what not to do.
You might even try sending yours in, but please don’t repeat the mistakes of others if you want any hope of getting a response. Better is to read every previous entry and learn from them to create a solid query letter that is going to wow an agent or editor and have them banging down your door to get some sample chapters. Give the site a look. It has the potential to drastically improve your query skills and likelihood of success.