A good place to start learning about magical timing is by working magic in conjunction with the moon. You can work with basic phases (waxing, waning, full, new, and dark) or you can work with the moon’s phase and the astrological sign it is passing through.
The new moon is for new beginnings, and starting projects.
The full moon is good for most kinds of magic, cleansing, raising power, and charging crystals and magic mirrors.
The waxing moon (between new and full) is for growth, building and increase.
The waning moon (from full to new) is for banishing unwanted energy or habits. Also things that need to decrease.
The dark moon (the day before the new moon) is good for working with ancestors, resting, and introspection.
This is not by any means a definitive list, and if you really like to keep things simple you can just use two phases: waxing-from the beginning of the new moon to full, and waning–from just after the full moon to just before the new moon.
Working magic when the moon is in a sign that corresponds to your intention, packs an even bigger punch. Many books on magic and astrology can tell you the significance the moon has in each sign.
There are times when the moon is considered to be void of course. This is a period of time when the moon is between signs. This can last for a few minutes or most of the day. It is best to not do magic or make major decisions at this time.