Benefic when waxing (shukla paksha) or well-aspected and bright; malefic when waning (krishna paksha), dark, or afflicted by the nodes or Saturn.
Reading
The Moon is the graha whose class is decided by its phase. A waxing Moon is saumya and gives the benefic reading; the waning Moon is krura, and the classical texts call the dark Moon a malefic without qualification. This is the single most important qualification in the whole benefic/malefic classification.
Karaka
MindManasMotherEmotionsPublicMemoryBloodWaterMilkFluidsSleepBeautyLeft eyeChestLungsNorth west
Chandra is the Moon, the graha of the mind (manas), the mother, the emotions and the public. Because the mind is what Jyotish reads most closely, the Moon's sign, nakshatra and phase are read beside the lagna, and a whole chart can be taken from the Moon (Chandra lagna). It rules Cancer and is the karaka of the 4th house.
Chandra is the Vedic moon, the cup of soma and the lord of plants, whose waxing and waning is a story of the gods drinking him down and the sun restoring him. He rules the mind and the night and the growing of everything green.
Modern Practice
Chandra is honoured at the full moon and in the planting of anything green. His practice is the lunar month kept, and the offering is white and cool.