You've made your decision, but now you may have no idea what comes next. Find out what the laws of your state are. It is essential that you find the laws and follow them. Most of the time, no one will check, but you don't want to find out the hard way that you're going to be the exception. Most states will at least require you to register in some way, keep attendance records, list books and materials used, and describe what you taught.
Many states also require some sort of evaluation each year.
Keeping notes in a dayplanner will give you the basic records. If your children have been receiving special education services, or if you think they need them, make those arrangements with the public school. Homeschoolers are legally entitled to receive special education services from the public schools if the child qualifies. You helped to pay for them, so don't be shy about asking. Bring a written copy of the request to give them.