Determining atomistic configurations is the first step to atomistic modeling of materials properties and often the goal of experimental characterization. While a myriad of computational tools have been used to determine, from first principles, thermodynamically stable atomistic configurations, quasi-equilibrium configurations are less explored. In addition, the combined usage of experimental and computational data has great potential for accelerating the determination of atomistic configurations. In this talk, I will discuss various techniques that combine first principles computation and experimental information to determine atomistic configurations, in some cases for non-thermodynamic equilibrium situations.