Determining SUSY and Higgs Parameters in the MSSM and its Extensions

If supersymmetry (SUSY) is realized at the electroweak scale, its underlying structure and breaking mechanism may be explored with great precision by a future linear $e^+ e^-$ collider (LC) with a clean environment, tunable collision energy, high luminosity polarized beams, and additional $e^-e^-$, $e\gamma$ and $\gamma\gamma$ modes. We review a few recent developments for determining fundamental SUSY and Higgs parameters, measuring CP violating $H/A$ mixing in the decoupling regime and probing the next--to--minimal supersymmetric standard model at the LC.