Vedic, the oldest incarnation of astrology, laid the foundation for all subsequent schools of astrology. It is also the most elaborate system and it draws upon the old Vedic scriptures. Astronomy and Astrology used to be united as one common science. The old Astronomic scripture Surya Siddhanta describes the orbits, mass and speed of the orbs. The estimations made have less than 10% error margin when compared to today's most accurate scientific measurements. What's more, the text (which was obviously written long before Columbus) also described that not only Earth, but also the universe is egg-shaped (Link:Earth is round Sanskrit Bhu Gola).
The 2 most important scriptures in astrology are Brihat Parashara Hora Shastra (by Parashara) and Upadesa Sutras (writen by Jaimini). Parashara describes subjective reality (how we feel) and Jaimini describes actual life facts (what will be my profession, how many children will we have, will we get married, etc.). The last part of Upadesa Sutras was discovered only recently and was written in coded Sanskrit. The correct translation and interpretation of just one line of these scriptures can take up to several years. Part of the scripture was coded, allegedly so it wouldn't fall into the wrong hands, so the knowledge could not be abused.
Vedic astrology can allow you insight into certain life patterns which are in part Karmically determined. The goal is to identify these patterns and to correct where necessary. It can help you to follow your heart and do what you came here to do (dharma). Many people let their actions be guided by either loved ones or by social norms and values, which can lead to depression.