The best place to begin is at the end: What do you want the “end product” to look like? In other words, what is your goal? When your child stands before you, having completed your program of study, what do you want to see?
Once you have your goal set, the next step is to determine what route you want to take to get there. How do you want to approach your child’s education? Yes, you have a choice; you don’t have to teach the way you were taught in school. Most homeschoolers use one of six basic approaches. Some parents use a combination of two or more approaches, choosing their favorite aspects from each. The six basic approaches to homeschooling are: traditional, unit studies, principle, unschooling, classical, Charlotte Mason. Once you determine which approach you prefer, you can find curriculum and book publishers or distributors that cater to each of the approaches.
As far as legal details go, check with the Home School Legal Defense Association to find out what the homeschool laws are in your state or province.