To make things flourish and grow, do a spell during the waxing moon — from the first day of the new moon to the first day of the Full Moon. At this time work for an increase of anything, or to diminish something.
To decrease anything do a spell during the waning period of the moon. This is a good time to get rid of any bad situation, including illness.
To put a stop to anything irksome, choose the second day of the Full Moon. Use silver and white to establish a link with the Moon.
–A Book of Pagan Rituals