Book excerpt: Astrology is a great science based on sound principles and theory of karma through cycles of rebirth. A horoscope is basically a map of zodiac indicating position of planets in various signs/ Nakshatra at the time and place of birth. The delineation of a chart is the science and art of deciphering it as per the knowledge, intuition of the astrologer and divine help available to him. Therefore the first requisite is to have sound knowledge of nature and characteristics of houses, signs, Nakshatra and planets and their inter-relation. Next comes the basic tools like dasha, transit, yoga and divisional chart and their application in delineating a horoscope. Lagna is the single most important factor in delineating a horoscope. It is the very being of the native, his élan vital & basic potential. Unless the seed of a specific quality or event is contained in this basic potential, other planetary indications will not find suitable opportunities for manifestation. Lagna also determines the numbering of houses with lagna being the first. With the change in lagna, the significations of any planet will change drastically, as his house & lordship changes, although the sign & constellation of the planet remain unchanged.