It's important to keep track of all your submissions to magazines, publishers and other places. Keep a file of when, where and what you submitted and if it was accepted or not. When a piece is not accepted, you can tweak it and resubmit to another publisher. Always check to make sure they haven't recently published your topic.
Research for your book...
Have you ever thought that you can research wherever you go? Be aware of your surroundings and take advantage of opportunities to pick up brochures, pamphlets, take photos or talk to locals. Keep a little notebook with you at all times. You never know when you will use the information.