So you've finished your last book and it is sitting in the inboxes of half of Manhattan and you are anxiously awaiting news of any sort because you're in this funky sort of limbo state. If the book sells, the editor will want you to revise and you will need to go back in the heads of your previous characters, so you can't possibly dive into something new because that would be practically schizophrenic switching gears like that, right?
Put down the chocolate and log off of Facebook and stop your procrastibaking, my friends. This is what is known as an excuse. Because the truth is: there is no more important time to be writing than right now, while the book is out there. If it sells, editors will want to know what else you've got. Your agent certainly will too, as their relationship with you hinges on your ability to produce more books, not just the one. And because the process takes so long to go from offer to actual publication, there is more than enough time to get seriously knee deep in the next thing so it will not be years between projects and you can strike while the iron is hot.
Even if you can't manage to get the words on the page, begin to research and map out the project. I like to buy a fresh spiral notebook that I dedicate to that project and start to take notes. I write down ideas, scenes, snippets of dialogue, great quotes I find that might suit the story and somehow find a way to be worked in later, ideas on theme - anything I can think of. It makes it so much easier when I sit down to write to have even the vaguest sense of who these characters are going to be and where I want this to go.
That said, I am a total pantser. Often when I start to write, I am working off of a zygote of an idea, and it's my characters that end up taking me the rest of the way there. Other people make charts, or use Save The Cat or Scrivener or Plot Whisperer tecniques. I use it all, but at different times and as needed. But first, I start with characters and setting. Who are these people? What attributes can I give them that make them unique and interesting and quirky so that they will stay with the reader long after they have finished the book? What can happen in their lives that will make a reader want to keep turning the pages to find out what happens next? What do they want and what is at stake if they don't get it? What (or whom) is standing in his/her way? Setting is important too, so where is the best place for this story to unfold? Is it someplace familiar to me or do I need to do research? And last but not least, are there other stories out there in the same vein as the one I would like to write? Or films? I begin to draw up lists and start to review them all to make sure I am not inadvertently duplicating something that already exists so I can make sure my take on things is fresh and fun.
The best part is finally diving in and meeting these new characters and finding out who they are and what they have to say. Immersing myself in their world helps me to forget the inevitable angst and anxiety of focusing on the last book and wondering when something will move with it in the ways that I am hoping it will. And when the other book does finally sell, getting back in the heads of those characters will be like meeting up with old friends.
This limbo time is precious. Don't waste it. DO take a break between projects, to clear your head, regroup, celebrate, and dust. (I can usually write my name in it by the end of a project: true story.) But then get busy.