If you are looking for a good time to begin something important or just want things to go smoothly for you, check out the phase and position of the moon. For about 2 weeks after the New Moon, it is said to be waxing, and it is a good time to begin things that you want to expand. Especially the first 2 days after the new moon.
For approximately another 2 weeks after the Full Moon it is said to be waning, and new projects may not grow as well.
Another factor is the sign the moon is in on the day in question. The moon goes around the zodiac once every month and stays in each sign approximately 2 days, but it varies every month and can be longer or shorter. Ideally, if you can, the best time to go for something is when the moon is in your Sun Sign. On the other hand, try to take it easy when the moon is in the sign opposite your sun. I will include a list of opposites at the end of this post.
Last but not least is the void-of-course moon. After the moon makes its last major aspect in one sign, before it enters the next sign it is said to be void-of-course, sort of wandering aimlessly, and things often don't go as planned. Again, this can last a few minutes or longer, it's different all the time.
So here's the list:
Aries - Libra
Taurus - Scorpio
Gemini - Sagittarius
Cancer - Capricorn
Leo - Aquarius
Virgo - Pisces
You can find the current moon phase at this site:
And here's a site that lists moon sign and void-of-course times:
Don't make yourself crazy, but if something's important it wouldn't hurt to try to choose the best time.