In this paper, various currently used methods to analyze and reduce non-tectonic noises are presented, such as power spectrum analysis, maximum likelihood estimator, regional stacking, principal component analysis, and deformation modeling under the loading of surface water/atmosphere mass. These methods are useful in deriving the spectral indices and amplitudes of colored noises, and helping understand the physical sources of the common-mode errors. The pros and cons of various techniques, as well as the future research directions, are also discussed.