Rule 1: Mutual comparisons(Sun-Sun, Moon-Moon, Mercury-Mercury, etc.) are the strongest. Rule 2: Interfunctional comparisons(Sun-Moon, Sun-Mercury, Sun-Venus, etc.) can make up for mutual incompatability. Rule 3: The sign, element, or gender should be used in terms of assessing the harmony or discord between two planets or signs. Aspects by degree intensify the effect. Rule 4: Both the planets and the signs should be compared when assessing compatability.