As always your own level of consciousness and honesty with yourself and your partner is the key to success. I don't know about you, but I often catch myself groaning over a couple in a movie or book getting themselves in the most complicated entanglements just because they don't speak up and communicate honestly. If they just would speak up they would have a better chance in working things out.
It makes sense, then, that the most potent example of astrological synastry (harmony between two birth charts) involves contact between one person's Sun and the other person's Moon, or contact between the two Moons. Carl Jung, the renowned Swiss Psychologist, famously conducted a 'marriage experiment' in which he studied the birth charts of over 500 couples. What he found was an unmistakable trend of Sun-Moon contact between partners. To most astrologers, this came as no surprise-it has long been understood that when one person's Moon hits another person's chart in a significant way, there exists a strong possibility of lasting and meaningful romance.
The influence of the moon on the Zodiac is a study in and of itself. When you are aware of your sun sign, you can use information about the cycles of the moon and the moon signs to determine the best time to make decisions or avoid certain activities. The moon signs are named the same as the Zodiac, but do not coincide with them.