Are You Ready To Submit Your Novel?
First there is the work itself. Is it going to grab the readers and therefore, an agent? Is it edited to the point where it looks professional and clean? Is the story strong enough or original enough that the agent will be able to not only enjoy it, but foresee selling it? These are very important questions that you must ask yourself.
Second is platform. Who is your audience and have you conveyed the book well enough that they will want to read it? Is it good enough that they'll recommend it to others? People buy and support books that grip them and make them feel something. Make sure you've tapped into that and you know how to convey it in your query. Have you made an attempt to connect with the people who will buy your book? Do you blog, Twitter, Facebook, or other social network that gets you in touch with your audience?
Third is the end all. Is your book going to make a publisher, and therefore an agent, money? The answer has to be yes or you aren't likely to get either. Will it be marketable in other avenues such as movies, graphic novels, video games, etc? It doesn't have to be all those things but if it can then great. The most important thing you have to remember about your book sales is that you MUST self promote. Publishers don't pay for promotion like they used to. Chances are you may not get any money for promotion at all. Be prepared to do your own. Have a plan.
For some great tips on what to know before you query check out this post by Jane Friedman of Writer's Digest.