How do I register for sales tax and determine on what to charge?

You must contact the State Department of Taxation where your business is located. Sales tax is a tax charged by various states on the sale of products or services? You must register with that state and every state's rules are different. Contact a CPA in your state to determine your responsibilities. As a business owner always remember, you are personally liable for sales tax not remitted properly, whether you collect it or not. So get yourself a good CPA.