The radial velocity (RV) technique has proven to be one of the most successful methods to search for extra-solar planets and is the most robust means by which to measure their masses (and therefore to infer their compositions). In this talk, I describe a set of routines to precisely measure relative velocities of stellar sources with the RV technique by measuring the Doppler shift from high resolution stellar spectra. I highlight results from a variety of spectrographs covering the optical, J and H band, and K band regimes. I also discuss one of the primary challenges plaguing RV measurements - stellar activity.