Q.Christmas cactus
On page
www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/how-to-propagate-and-plant-christmas-cactus.htm
it says:
“…taking a short, Y-shaped cutting from the stem tip..”
What does that mean?
The best cuttings are those that have two smaller segments growing from one segment, thus a Y shape, as in some of the pictures of the cuttings on this page:
http://vitalifeliving.blogspot.com/2013/07/christmas-cactus-cuttings.html
However, if you can't find this on your plant, a cutting that includes 2-3 segments growing in a straight line instead of a Y shape should also root.