We propose the use of generalized boundary layer equations and governing dimensionless parameters for mixed convection of either the forced-convection-dominated case or the free-convection-dominated case. Such equations are derived by considering the asymptotic limits of high Reynolds number or high Peclet number, and high Rayleigh number or high Boussinesq number, with small or large Prandtl and Richardson numbers as the case may be. Here, we illustrate the ideas in the forced-convection-dominated case in the small Prandtl number limit. We show that the exercise provides a more convenient format for displaying the results of computational or experimental investigations of mixed convection, leading to more general quantitative results as long as the asymptotic conditions are met, and possibly general qualitative results even when the asymptotic conditions are not strictly satisfied. In addition the contributions of normal and tangential buoyancy are also clearly separated.