How do I become a certified yoga instructor?

I am interested in becoming a yoga instructor, specifically for prenatal and mommy and me yoga (also known as Itsy Bitsy Yoga in some places). I used to do yoga all the time and I am now getting back into it and my love for it keeps growing. I know it will take a long time, and I am starting by taking regular Hatha Yoga classes, I just want to know the steps I will need to take, and any tips from anyone who has been there.