Okay, your manuscript is done...finally! Now, you can't wait to hop in your car and mail it off to all those editors whose names you've been collecting and coveting.
Stop! Wait...trust me on this.
Don't do anything for two weeks...and I mean it. During those two weeks, don't even think about reading your manuscript. Instead, return all those phone calls you've been screening, pay your bills, treat your honey to a great evening to make up for all the time you've ignored him or her while you've been writing.
Then, after those two weeks have passed, read a printed copy of your manuscript. Reading print copy rather than screen copy will allow you to see your work in a new light. And it will highlight those little mistakes and inconsistencies that were previously overlooked. Believe me when I tell you, they are there.
Once you've inputted those corrections, spend the money to make three more copies of your manuscript. Find three people who can and will read your manuscript and give you brutal, honest, unadulterated feedback. Give one to each on your list. Tell them to feel free to mark the copy, note comments, raise questions, and circle typos (trust me, there will be at least thirty more).
When the friend(s) are done, meet with them, individually. Put your ego and emotions aside and listen to their comments. This is your reading public. And their initial critique could mean the difference between a sale and a rejection.