There are eight astronomical phases of the Moon, but magick generally focuses on three that are considered to be particularly significant.
The waxing moon: As the Moon is increasing in size, it is said to be waxing. The light increases, appearing to spread from right to left, and this phase lasts right until the moment that the Moon becomes completely visible – the full moon. The waxing phase is the time for magick for increase or to attract good things. The more the Moon increases in size, the more powerful become its energies to attract abundance.
The full moon: The full moon phase, when the whole of the Moon is visible, is the time for the most potent magick, but it lasts for only 24 hours – although, as I have said, most practitioners allow a day on either side.
The waning moon: From the second following the 24 hours of the full moon, the Moon is waning. The light decreases as the Moon shrinks from right to left and the energies too start to wane until the Moon is no longer visible at all. The wane is the time for banishing and for decreasing influences. The more it decreases, the more the potency decreases, so the pull that keeps any destructive influences in you is also decreasing. You can, however, use the waning moon like an emptying bath and wash away all the bad things into the cosmos or the earth as the energies swirl away, to be restored and reformed into positivity.