This chapter reviews the basic ingredients of simulating relativistic nuclear collisions, of which fluid dynamics is one component. Nuclear geometry models with and without subnucleonic degrees of freedom are discussed, energy deposition at weak and strong coupling is reviewed and found to lead to similar results as the simple Glauber model with number of collision scaling. Initial state eccentricities are calculated, numerical algorithms to solve relativistic dissipative fluid dynamics are discussed and the freeze-out from fluid to particle degrees of freedom (hadronization) is described. The chapter closes with a discussion on how to calculate relevant observables in relativistic nuclear collision experiments.