Here is a short video to tell you why to pull up the bobbin thread and also how to do it.
There have been times when for whatever reason (lazy?) I have not pulled up my bobbin thread. After I have merrily quilted along, I turn over my project and (sad face) I have a tangled mess in one corner where the bobbin thread was and now I have to attempt to pull it out. Don’t find yourself in this situation!