The waning moon is the period during which the moon goes from full to dark once again. Like the waxing moon phase, it lasts approximately two weeks. In many traditions of Wicca and Paganism, this time of the month is used to do "baneful" magic -- that which sends away, gets rid of or destroys things you no longer wish to be burdened by. Some examples would include:
Magic to eliminate negative or toxic people from your life.
Workings to smoothly end a relationship, job, or living situation.
Rituals that banish bad habits.
Any magic related to reducing things, such as debt, illness, etc.
shedding old patterns