I took some sewing classes when I got my new Jenome. They talked about thread and told us that if the thread is wound in a diamond pattern on the spool it can be used either on the vertical or horizontal stem holder. Otherwise it should be in the vertical position.
Also don't pull thread out of the machine by pulling on the spool. Cut the thread and pull it out from the needle. This is a hard habit for me to break! I understand it's all because of the computerized machines.