Probing light dark sectors via new macroscopic forces

New dynamics from light and weakly-coupled sectors beyond the Standard Model may manifest as long- range forces between visible matter particles. Such new forces can be searches for by means of a variety of experimental approaches. In this thesis, we re-examine the calculation of non-relativistic potentials mediated by new light particles coupled to the Standard Model, employing a general parametrization of the new interactions and going beyond the leading order Born approximation. We correct and integrate previous results, and point out as well the presence of new relevant contact terms arising at next-to-leading order in the non-relativistic expansion.