If you've written your first novel and submitted it to a couple of publishers, you're might find yourself at a loss. What do you do now? You could do any number of things, really. You might choose to take a break and wait for the results of your queries. Maybe you'll sit in a chair and fret about the queries you sent out. but neither of these is very productive.
Instead, keep your work out there. Look up every publisher that specializes in the genre of your novel and submit more queries. If you're looking for an agent, fire off queries to as many as you can find. Keep at it until you've submitted to every publisher and agent with a publicly available address. If you don't keep your work out there, you'll never be a published author.
For those who've chosen to self-publish, you'll have to promote your work to get any sales at all. With the Internet, this has become easier, but it still requires effort. Promote your book on social networking sites, link exchanges, and anywhere else you can think of. You might also want to consider approaching your local bookstores about stocking the book. This is harder than it sounds, as many bookstores are reluctant to carry a self-published work. However, with a little persistence, you might be able to change their minds.
If you really believe in your book, keep it out there. If it's truly worth publishing, someone will publish it. And if it's well written and entertaining, people will buy it. But it's up to you to make sure your novel stays out there, getting attention and hopefully being noticed by the right people.