We came to know almost two decades ago that their are other planets orbiting their host stars like solar planets. The Kepler mission of NASA has discovered thousands of such planets and planet candidates during its mission. Many more space missions, in coming years, will increase this number. Ground based follow-up observations can help in confirmation and characterization of these exo-planet candidates. Such a large number of exo-planet systems can help us in testing present planet formation and evolution models. In this talk, I will discuss about five observational techniques that are presently used in the detection of exo-planets: Doppler method, transit photometry, direct imaging, microlensing, and astrometry. I will discuss about basic description of how each of these techniques works and what is the role of ground based telescopes in exo-planet discovery.