You can use switchwords in any way that resonates with you. As a witch, I would decide what energy I wanted to tune into. So, if I were trying to get rid of an unwanted condition, it would be a good idea to do it during the time of the waning moon. If I wanted to attract love or money, then a waxing or full moon is a good time.
If someone isn't witchy, then they can use them any time they like. It's not important.
If you want to burn the paper that you write the words on, then do it safely.