1. Plan your exit. Basically, think business plan but for closing your company. Make sure you have a protocol to handle each situation that may happen.
2. Visit the website for the IRS. Depending on how you have your current business classified, shutting the doors may not be the only step needed to end the business relationship with the government. LLCs and corporations have to file specific documents. The IRS offers a free checklist to help you.
3. Maintain your records. Don't close shop and burn your records. You still may need them. Keep all your files locked away for at least three years.
If you need advice on how to close a business or if you should close a business note that I'm available as a resource. There is a fee but mention this blog for a special rate.