There are some important steps to getting started on homeschooling. First, you need to research your state's requirements for homeschooling. The HSLDA has tons of information on the legal issues of homeschooling, and here is a page where you can check into your state's standards. Also investigate homeschooling groups in your area--they can be a great resource, especially for new homeschoolers.
Once you make sure you're in compliance with any state regs, it's important to choose or create a curriculum that will work for your family and keep your child on track academically. Since I was going to be making our curriculum, I researched the state standards for public schools and based my curriculum on making sure we'd meet and exceed all the minimums for his grade. Many states list their standards online, but if not, you might be able to request that information from the school system or you could use another state's info as a rough guideline. I've noticed that a lot of grade level workbooks and curriculum vary a lot depending on publisher, so I like knowing the state framework when I screen workbooks and search for worksheets.
That being said, don't get too bogged down in the state standards. Basically, I use the frameworks as an overall goals list for the school year, but we work at a pace that is right for us and we learn the topics in an order that makes sense to us. This year, my son is working mostly on a 1st grade level, but also learning some things that he would have learned in Kindergarten in public school as well as some concepts that wouldn't be introduced until 2nd grade. That's one of the best things about homeschooling--you teach at a rate your child understands and you can do it in a pretty short time period each day.