I'm submitting right now. Or rather, my agent is submitting my new novel to a dozen publishers.
Submitting manuscripts to publishers is one of the main reasons writers have agents. Agents know publishers, and the types of books they're looking for. They also know how to get the best deal.
These days, submissions are electronic. No more making copies and Fed-Exing or messengering them around NY. Agents send electronic files, and the editors print them up. This saves time and trees, and hopefully shortens the response time.
Responses do take time. Depending on the buzz around the book (your agent should have talked it up to editors before sending it to them) and the star-power of the author, it may take a few days to a few weeks (in some cases, even months) for the editor to read and respond.
Hopefully, a publisher will make an offer. This usually involves an editor bringing the manuscript to an acquisitions meeting, where her peers (fellow editors, bosses, marketing people, sales people, accounting people) decide whether or not to try to acquire a book.
These meetings (called "ax" meetings) rarely result in offers. Even if an editor adores a book, the house can still vote no. This depends on a variety of factors: author sales record, publisher sales record with similar books, new and passing trends, buying habits of chains, and many other things. I've heard that 4 out of 5 books brought to ax meetings die there. So even if the editor thinks your book is wonderful, there's still a 80% chance they won't offer a contract.
In the meantime, the author waits. Chewing fingernails. Jumping whenever the phone rings. Dreaming of huge deals and fearing no deals at all.
If you aren't normally neurotic, being on submission will make you so.
So what should this neurotic author do while waiting for the yes or no?
1. Write. You're a writer. That means you put words on paper. You shouldn't stop doing this just because you're anxious.
2. Talk. Bottling all of this anxiety up isn't healthy. Share it with family, friends, and peers.
3. Leave your agent alone. Bugging her constantly, asking for updates, is annoying. If she has good news, she'll call. Assume that no news means she hasn't heard anything yet.
4. Relax. This is easier said than done, but be Zen about it. You've done all you can. It's out of your hands. Worry, stress, prayer, hope, wishes, and dreams aren't going to do anything for you. Don't try to control the situation, because you have no control over it.
I won't sugarcoat it. Being on submission is awful, right up there with being between contracts. The unknown is scary, especially when this is how you make your living. That's why politicians spend so much money on election campaigns. Not having job security is terrifying. So is rejection.
Which is why you need to get back to work.