I have always just taken a cutting about an inch below a set of two leaves, dipped it in root tone and put it in soil in the windowsill. They've always taken root. The tricky part is acclimating it to the temperature outside if you live in a climate where the spring can be quite cold or if you are putting it outside in the summer after keeping it in A/C. I have taken many cuttings from my grandmother's and neighbors hydrangeas. They are pretty easy to grow. I usually start with really small cuttings and keep them in the window in the kitchen for about an entire year to give them a good healthy start. It seems to work best for me if I don't have a large cutting so the plant doesn't have so much to feed before it gets properly established with a solid root system. Root Tone is the key.