ask lots of questions. get your hands on as many different curriculums as you can...pour over them, pay close attention to the types of things they are being taught...see if what they are being taught they are understanding and if not, take note of that. If you can visit others who homeschool, do...see their set up, see how they do things, again ASK LOTS OF QUESTIONS.
We decided to homeschool a week before school was to begin, so we put our kids in school for 1 semester, and I used that time to prepare and get ready....so I did the very thing I suggested up above...but I honestly wished I would have been able to see more curriuclums first...because I have tried several and have found some that really like, and other...not so much. But, that is ok..the beauty of homeschool.
Good luck on your decision and your preparing.