Yo Spuds! I usually wait until the center stem is about 6 inches tall and still nice and flimsy. I use coat hangars as hooks and push them into the media first and then very, very gently bend the stem over and place it under the hook part. The point is to get the top of the plant LOWER than the part of the stem that is bent. That way, hormones are sent to the "tallest" point of the plant, that point now being the curved stem, not the top that you bent over. This will make the shoots that are growing from the stem grow much faster and give you more tops.