In this thesis we investigated the effect of the chemical environment as well as different theoretical approaches in predicting the surface enhanced Raman Scattering-charge transfer (SERS-CT) spectra. The discovery of SERS and its enormous enhancement factors in 1974 raised questions about the underlying enhancement mechanism. The charge-transfer mechanism of SERS is believed to be the fundamental mechanism creating the distinctive pattern of SERS and is local to the adsorption chemistry of the molecule. However, the challenges of SERS-CT experiments make it difficult to study the effect of each of these variables on SERS-CT selection rules. Therefore, computational modelling of the SERS system and its environment is a crucial part of understanding this mechanism. A thorough computational study of SERS-CT calls for detailed assessment of different approaches, approximation and methods involved in calculation of the spectra. In this thesis we have used the time-dependent approach to the transition polarizability that is used to calculate SERS intensities and treated the excited PES the same as the ground state, only with a displaced minima. In chapter 3, we have investigated the chemical nature of benzene-like derivatives on the pattern of SERS-CT spectra measured at different electrode potentials. The results are compared with the experiment and the computational factors involved are analyzed. In chapter 4, defining factors in the adsorption chemistry such as direction of the electrode potential and adsorption orientation and bond length are investigated for Pyridine. In chapter 5, we have investigated the vibronic coupling effects in SERRS spectra by calculating the Herzberg–Teller contribution to intensity for 4,4′-Diaminotolane. Finally, chapter 6 investigates resonance Raman spectra for various organic molecules using the density functional tight-binding (DFTB) method as an efficient approximation to DFT methods. In this thesis we have shown the validity of the employed theoretical and computational approaches in predicting resonance Raman and SERS-CT spectra, which makes this approach a reliable candidate to accompany studies of chemical enhancement and selection rules of SERS. In addition, the considerable contribution of the Herzberg–Teller term to the intensities is an interesting case that shows the limitations of the frequently used Frank-Condon approximation. This encourages us to seek this contribution in other challenging systems with dominant CT effects. The acceptable performance of DFTB method in predicting the resonance Raman spectra opens a window of opportunity for the resonance Raman and SERS study of model systems with more realistic substrate size and large biological molecules, on its own as an initial step or combined with ab-initio or molecular dynamic methods.