  We approach the following question: if supersymmetry is discovered, how can
we select among different supersymmetric extensions of the Standard Model? In
particular, we perform an analysis of the sparticle spectrum in low-energy
string effective theories, asking which observables best distinguish various
scenarios. We examine scenarios differing by the fundamental string scale and
concentrate on GUT and intermediate scale models. We scan over all parameters
(two goldstino angles, tan beta and the gravitino mass) in each scenario,
finding ratios of sparticle masses that provide the maximum discrimination
between them. The necessary accuracy for discrimination is determined in each
case. We find that the required accuracy on various sparticle mass ratios is at
the few percent level, a precision that may be achieved in future linear
colliders. We also map out phenomenologically viable regions of parameter
space.
