First and foremost, read about the requirements for homeschooling in your state. The Homeschool Legal Defense Association (HSLDA) has this handy reference on their site. In our case, we submitted a simple form online to our state's Department of Education, and then provided a copy of it to the school we were withdrawing from.
Next, although I'm sure you've read everything you can get your hands on, You will want to do some more reading about different homeschool styles. Tracy wrote a great post about defining your homeschool style. I remember reading this simple list of styles when I first got serious about the idea of bringing the kids home. There will not be only one that will fit your family (probably!) but knowing what all these terms are referring to will really help you decipher a great deal of the information you are going to encounter when you get serious about choosing curriculum. It will also give you a general idea of the direction you are interested in taking with your family's homeschooling journey.
Once you feel you have a good understanding of your state's requirements and the basic homeschool styles, you will want to look deeper into curriculum. Here is a site that has reviews written by homeschoolers who have actually used the product being reviewed, which I found to be very helpful when I was first considering curriculum. I also highly recommend going to any used curriculum sale or swap you can - this is a great opportunity to put your hands on copies of the materials you are interested in, and speak with someone who has used them as well.
It's important to consider your budget when you are looking at curriculum. I had some pretty serious sticker shock when I began pricing them! Then I started thinking about the things we had been spending money on that we would no longer need - school uniforms, textbook/technology/enrollment fees, school lunches, snacks/party items supplied to the class, gas to and from school each day, four different fundraisers each year, gifts for teachers and holiday exchanges, tickets to the school play each year...you get the idea. Pretty soon I realized we could afford the curriculum I had fallen in love with. There are lots of great resources for homeschooling for less or for free, like this book, or this one, if you are working hard on saving money while homeschooling.
Most importantly, take some time to decompress as a family. Read a bit about deschooling. You are getting ready to embark on a great adventure; a fantastic journey. It is a very big leap to move into homeschooling if you have been in an institutional setting, and it requires courage to do so. Spend time just having fun together in the ways your family loves best - no planning, no pressure, just being yourselves. As you plan your first year, take a moment to write down your reasons and goals for homeschooling. It will be a wonderful memento to look back on, as well as a source of great encouragement on the days that are tough. Best wishes!