Depending on your spell, you should aim to cast it in
harmony with the cycles of the moon to achieve the most effective results.
Below are the phases of the moon, what they mean, and what sort of spells
are good to do during each phase.
The new moon is the
beginning of the lunar cycle, and means that the moon is completely in
line with the sun and the earth. We see a dark sky with no visible moon.
It's a time of newness and rejuvenation. The new moon is the three days
after the new face of the moon and also includes the day of the new face
of the moon.
Spells: New beginnings of any sort, beauty, health, personal
improvement or new employment.
The waxing moon is the period of time
between the new moon and the full moon. Every night, the moon gets a
little larger. Any spellwork that requires growth should be done now.
Spells: Courage, motivation, inspiration, friendship, elemental magick,
healing or luck.
This is a time when the Moon is at its
most powerful, and the magic most potent. Performing any positive spell at
this time will achieve good results. Since the full moon only truly occurs
for one night out of the entire lunar cycle, it can be hard to fit it into
your schedule. You can harness the energy of the full moon for about 2
days before or after the night the moon is truly full.
Spells: Artistic projects, love, romance, fertility, psychic abilities
or making decisions. Also healing, guidance, and completion spells.
The moon is waning as it gets smaller
again, after the full moon. As the moon seems to disappear in the sky, use
this time to do spellwork to remove things from your life. The waning moon
is a good time for the casting out of the old ways, banishing old habits,
smoking, eating habits, the removal of troubles and worries.
Spells: Banishing bad habits, addictions, or ending relationships
Typically, there is one full moon every month, but since
the lunar cycle is a bit shorter than our calendar months, there is
sometimes two. The second full moon in any given month is called a
I want to mention the Dark Moon here, also called "The
Dark of the Moon" because I find it very interesting personally. Many
witches do not bother themselves with the dark moon or are not aware of
the meaning of it. Below is a description of the dark moon.
Dark of the Moon - The Dark of the Moon (or Dark
Moon) is traditionally the last three days of the Lunar cycle, immediately
preceding the New Moon, and the time when the night sky is notably absent
the presence of the Moon. George  notes that: “The earliest peoples
understood that the power of life lay in the darkness of the moon.” “The
purpose of the dark phase of any cycle is that of transition between the
death of the old and the birth of the new. The dark time is a time of
retreat, of healing, and of dreaming of the future.” i.e. the fallow times
preceding outbursts of creativity and growth.
“Most of us do not realize we all have many dark phase
times in our lives, and that these are naturally occurring periods in any
life cycle. We fail to understand that endings are the precursors to new
beginnings; thus when our life rhythms move us into and through these dark
phases, we are ignorant of what is actually happening.”  It is the
grandeur of Death and Rebirth, not merely an ending with the proverbial
ride off into the sunset.
“The dark phase of the cyclical process is a phase of
healing and renewal rather than one of fear and unknowing; a time of
mystery, wisdom, and healing power -- all gifts of the Dark Moon Goddess.”
“There is less energy available for outer activities and
meeting the expectations of others, because the purpose of the dark phase
is for focusing on the inner dimensions of our bodies and minds. If we can
learn to attune ourselves to the natural rhythms of ebb and flow in our
lives, we can use the intrinsic function of the dark times for healing and
renewal. When we resist this inward motion in our psyche, then anxiety,
stress, and fear are more likely to take hold of our emotions.” 
“The Triple Moon Goddess, in her new, full, and dark
phases, was a model for the feminine nature in her entirety as maiden,
mother, and crone. In her original worship the Dark Goddess, as the third
aspect of this lunar trilogy, was honored, loved, and accepted for her
wisdom and for her mystery teachings of renewal.” 
Spells: Healing, renewal, psychic spells. A good time to meditate on
the inner self.
 Demetra George, Mysteries of the Dark Moon, The Healing Power of the
Dark Goddess, Harper San Francisco, 1992.
More Resources for Spellwork
Color Correspondences for Spellwork
Daily Planetary Correspondences
How-to Articles (Write Your Own Spells, etc.)
Articles Free Spells