Small Business and Self-Employed Tax Center - The small business and self-employed tax center is a page of the IRS website that helps small business owners find all of the necessary tax forms and documents. Artists can register their business and apply for an EIN (Employer Identification Number) that allows them to hire help. Artists can also find important forms for filing their yearly income tax.
Artists who plan on pursuing a full-time art career need to register with both state and federal government agencies to be able to collect sales tax and file income taxes. Many art shows do not allow artists to participate unless they have the required state documents to collect the sales tax. It's also just important to be professional to prevent any future problems with audits.
The small business and self-employed tax center is a wonderful resource for anyone seeking small business tax information at the Federal level. Each state also has sites for small businesses though, and don't neglect viewing that information to be prepared as you start your business.
Square - Square is a service that will process your credit cards through your smart phone. Sign up at http://www.squareup.com/ and they will send you a free card reader. Use the reader with the Square app on your smart phone to process credit cards at shows. You will only need to pay a small credit card processing fee for each transaction, which is much better than paying a monthly fee AND a processing fee, like most credit card processing companies.