I cannot overstate this enough: do not submit a first draft.
The first thing you should do after typing "The End" and feeling the thrill of accomplishment is not open your email and start drafting your submissions letter to the publisher. No, the first thing you should do is edit your shit.
Yes, the publisher you submit to will very likely have editors on staff. However, it is not solely the publisher's responsibility to clean up your manuscript and whip it into shape. When you submit to a publisher, you're selling a product. You should do everything in your power to make certain that product is in the best possible condition.
I recommend the following methods:
1) Put the manuscript away (out of sight, out of mind) for a minimum two (2) weeks. Don't read it, don't poke at it, don't scribble notes. Just leave it alone and work on something else. Only after two weeks have passed should you even thinking about opening up that document and looking over you manuscript again.When you do, take an honest, critical eye to your manuscript. You're not just looking for typos, you're looking to fix everything. No first draft is ever perfect; don't expect yours to be. Be prepared to remove/revise/add large portions of the text. Also be ready and willing to do some additional research to verify/add clarity to some parts things.Even second & third drafts can be imperfect, so once the self-editing is completed you should then...2) Forward your manuscript to a beta reader/pre-reader/editor friend who owes you a favor. I strongly recommend having a beta reader of some sort on hand. A beta reader is, after all, a reader, and they will be able to give you comments/suggestions from the perspective of a reader. And if they're asking these questions now, the odds are good other readers will ask them later. So pay attention and take their comments to heart.Be prepared to make even more revisions.Note: Saying that you can't find a beta reader is not an excuse. There are all sorts of communities and groups out there for just that thing. If you hang out in places such as Twitter or Tumblr, it's usually as easy as posting a request. Odds are there are more than a few experienced, eager betas there who would be willing to help you out.
In the end, you should expect that it will be at least one month from the time you complete your first draft to the time you're ready to submit your manuscript. And that's if you rush through the edits.
Don't rush through the edits.
Take your time and be as thorough as possible. And don't assume the editor reviewing your submission won't be able to tell if they're reading a first draft. I would say little more than half of the manuscripts LT3 rejects is because of the editing (or lack of) and the fact that the manuscript is clearly a first draft.
Editing is a very important part of the writing process. Please don't skip it.