So...here we go:
How long is your book? Word counts of < 50,000 are considered novellas or short stories depending on length, while 90-100,000 is pushing the boat and 100,000 or over is too much. These all depend on what genre you're writing in, so check out this article for tips.
Where are you going to submit to? Different publishers offer different royalty rates, services and advice. They also have different submission requirements. You NEED to check this out, before submitting anywhere! Don't get your story edited to perfection in Times New Roman, 12pt text, with a 1 inch margin, if the publisher you're submitting to wants your work in Ariel, 10pt, with a 3cm margin.