In this paper we are reviewing results regarding the velocity tracking problem. In particular, we focus on our work (Casas and Chrysafinos, SIAM J. Numer. Anal. 50(5): 2281-2306, 2012 Casas and Chrysafinos, Numer. Math. 130:615-643, 2015; and Casas and Crysafinos, to appear in ESAIM: COCV) concerning a-priori error estimates for the velocity tracking of two-dimensional evolutionary Navier-Stokes flows. The controls are of distributed type, and subject to point-wise control constraints. The standard tracking type functional is considered, however the option of setting the penalty-regularization parameter D 0 in front of the L 2 .0; TI L 2 .˝// norm of the control in the functional is also discussed. The discretization scheme of the state and adjoint equations is based on a discontinuous time-stepping scheme combined with conforming finite elements (in space) for the velocity and pressure. Provided that the time and space discretization parameters, and h respectively, satisfy Ä p / for some p > 2, are discussed for the difference between the locally optimal controls and their discrete approximations, when the controls are discretized by piecewise constants functions, the variational discretization approach or by using piecewise-linears in space respectively for > 0. For the case of D 0, (bangbang type controls) we also discuss various issues related to the analysis and discretization, emphasizing on the different features compared to the case > 0. In particular, fully-discrete estimates for the states are presented and discussed.