Your spells will be given a powerful boost by timing them with the four phases, or quarters, of the Moon. You can choose to use this method alone or in conjunction with other spell-boosters, but whatever you do, it is best to at least time your magickal workings with the Moon phases, as they can either make or break your spell.
The Moon is said to be "waxing" during the period of increase from the New to the Full Moon. The Waxing Moon is a time for bringing your desires to you. The first quarter after the New Moon is the strongest period for attraction, as the Sun and Moon are working together to pull in the same direction, however you should wait until at least 12 hours after the start of the New Moon to do any spell work. The second quarter begins about seven days into the lunar cycle and, as the Moon is still in the waxing phase, is a good time for workings to add to something you already have in your life.
The period of decrease from the Full back to the New or "Dark" Moon, as it is sometimes called, is referred to as the Waning Moon and lasts through the third and fourth quarters of the lunar cycle. Spells are done at this time to remove, repel, or banish unwanted, negative things. Spells for getting rid of bad habits, breaking addictions, and losing weight are all appropriate for this phase of the Moon.
The Full Moon occurs when the Sun and Moon are on opposite sides of the Earth, causing the Moon to appear as a full and complete bright sphere, marking maturity and fruition. Spells that were put in motion at the New Moon begin to manifest now. The three days leading up to the Full Moon, the actual day of, and the three days immediately following the Full Moon is a time of great energy and power and is therefore often used for particularly difficult or complex workings. Spells of any kind will be given extra "umph" when performed during this time--just remember that the energy you put out will come back to you with extra force, so be ever-mindful that your intentions are good and that they harm absolutely no one.
Also known as the "Dark" Moon, the New Moon is a good time for spell work to begin new things. Just remember to wait until the initial 12 hours of the New Moon have passed.