We present our work in the field of transiting exoplanet systems. Our studies include ground based observations and techniques in combination with space missions (CoRoT & Kepler). In this Thesis, we present our results for transits theory and observations. We have built the Photometric Software for Transits, in order to handle ground based transiting data, and the CoRoT Detrend Algorithm to correct and analyze CoRoT light curves. Using the 1.2m Oskar-Luhning Telescope from Hamburg Observatory and the 2.2m Calar Alto telescope (with BUSCA CCD) we have studied the TrES-2b transiting system. Inclination change has been found after one year of observations (May 2008- May 2009) probably, because a non-transiting secondary planet. Also, using Tycho catalog we have calculated the transit probability of ~ 106 stars. We present probability maps of the full sky, for Hot Jupiters and habitable planets, as well. The probability for a Hot Jupiter using a ground based survey (e.g SuperWasp or HatNet) is smaller that ~ 13%. From space, using CoRoT IRa01 data, we calculate that the probability of habitable planets is high enough. We prove the eccentricity threshold of habitable orbits, which the maximum eccentricity emax = 0.397, is independent of any stellar properties. Finally, we present a method to extract information for the planetary system (e.g. planetary albedo, eccentricity, ω) using only the photometric light curve of the transit and Kepler's equation if the photometric accuracy is high enough, without any Radial Velocity measurements.