Question: How do you begin to reapply to college after your gap year? How do you obtain the old information submitted previously (e.g., counselor/teacher recommendations)?
I can't tell if you intend to apply to colleges to which you've already applied or to other ones, so I'll answer the question both ways.
First, if you're planning to take another shot at schools that already said, "No," then you've got an uphill battle ahead. It's uncommon to be admitted after a gap year to a college that turned you down. Your odds would be much better if you went elsewhere first and then reapplied as a transfer. But if you plan to reapply to colleges that already admitted you, then your chances of getting in are good. In any case, schools to which you applied as a senior should still have much of your old information on file, so your first step is to contact them and ask them what they'll need. But, as you do, keep in mind that a gap year can be an eye-opening, life-changing experience, so you may find that the colleges you applied to this past year don't "fit" you quite as well as you thought they did by the time your year-off is over.
If, however, you're aiming for new colleges, then it's a good idea to contact your high school guidance counselor right now and ask what materials are on file in the guidance office and how to access them in the fall or early winter, when your applications will probably be due. Your high school file may--or may not--also include the references you solicited from your teachers. If your school file does include these references, then the guidance office can probably send them out for you when your start to apply. If your file does not include references, then it will be up to you to track down your teachers and ask them to please send copies of their letters to additional schools. The smartest time to do this is now. The teachers probably still have copies of the recommendations they wrote for you, but they may not keep them for posterity. So warn the teachers ASAP that you'll need their help once again. You will also have to order SAT or ACT scores sent to the new colleges, if required.
Finally, whether you're reapplying to colleges that you applied to before or to brand-new ones, you should also send updated information that explains what you've been doing during your gap year, along with another more recent recommendation from someone who taught you or worked with you (etc.) during your time off.
Hope you have a wonderful gap year. "The Dean" wouldn't mind taking one, too. :-)