The most common mistake writers make in the query process is querying too soon. But how soon is too soon?
It's too soon if:
1. You just finished writing the novel. Writing a good novel isn't about writing; it's about revision. Revision takes time. If it took you a year to write the novel, it will take six months to revise it.
2. It's your first novel. No matter how hard it is to hear and follow this advice, it's probably the best advice I'll ever offer: write a second novel before you query on the first one. You'll learn so much while writing that second novel that you'll go back and either revise or discard Novel #1. AND you won't have all the baggage from those damn form rejections to weigh you down
3. You don't have a polished one page synopsis. Writing a synopsis is torture. I know it; you know it. It also is an incredible writing tool. If you can't get your book to make sense in synopsis form, you have a problem with the BOOK not the synopsis.
Your desire to get past the query stage to publication stage is the biggest block to actually achieving your goal.