I think this is a mistake we've all made at one point, and I made it under the encouragement of a published author, is we query too early. You've heard this a thousand times over, write the best book that you can. Well, that takes time, a lot of it.
- After you finish you first draft it is not ready for querying. It's not. No matter how much you love it. It's not. Distance yourself from it for a few weeks and then go back and read it. You'll see what I mean.
- Listen to that voice in your head. Often, we are perfectly aware of the flaws in our story and writing. And yet we push those voices aside and don't really listen to them until a critique partner or agent echos that same thought.
- The story just doesn't have to be spectacular, the writing does too. I've critiqued manuscripts where I'm like this is an awesome story, but then when you get down to the sentences, the words, they all need some tightening and polishing. Every word has to earn it's right to be there, so take the time to let every one of them shine.
- Don't be scared to re-write. In that first draft, you're just getting to know your characters, their likes/dislikes, and motivations. Sometimes you have to go back and delete scenes, add new ones, but it doesn't mean that what you wrote in that first draft was a waste of time. That was an important step towards learning who your characters are.