Avocado Planting

I always have one of these growing in our window. It's so exciting when they first sprout roots, and then send up a shoot that grows leaves and gets taller and taller. I cut them down, and they grow back again. But my problem is after that. Then what? I aspire to grow a healthy, green, multi-branched, leafy wonder. Not sure how to get there because usually if I transfer them into soil they don't make it. Any pointers?