Do you want to spend several thousand hours writing 250 words to sum up your novel you will inevitably change 250 thousand times? How about spending every free moment for writing on coming up with that perfect first sentence to entice anyone to read you manuscript? Maybe you're still editing and you'd like a nice break. Then you might be ready to start the query letter.
To transform your manuscript into the next great novel, you will need a crackerjack literary agent. And to find one of those elusive devils, they must be lured in with a query letter they cannot put down; a query letter that makes the agent beg for the manuscript.
The first step you must take toward writing what will hopefully be the perfect query, will be to research how to write a query letter. There are many excellent sources from which to choose, though I highly recommend QueryShark. There is no one better to help an aspiring writer with their best possible query letter than a literary agent and she doesn't mess around with morons. Read what she has to say about past letters, absorb all that you can from the hundreds of queries she tears apart, and then maybe you will begin to understand what is expected of you.
If you aren't willing to do the work (if you say 'yes' to this, you might want to look into another profession) then the best piece of advice I can give you when writing the query letter is to keep it simple, focus on what your protagonist wants, and don't for any reason start the letter with a rhetorical question.
Next: Should I just start a new novel?
