  We study the structure of the soft SUSY-breaking terms obtained from large
classes of 4-D Strings under the assumption of dilaton/moduli dominance in the
process of SUSY-breaking. In particular, we first analyze in detail the
dilaton-dominated limit because of its finiteness properties and
phenomenological predictivity, and second, we consider the new features
appearing when several moduli fields contribute to SUSY breaking. Although some
qualitative features indeed change in the multimoduli case with respect to the
dilaton dominance one, the most natural mass relations at low-energy $m_l < m_q
\simeq M_g$ are still similar. We also study the presence of tachyons pointing
out that their possible existence may be, in some cases, an interesting
advantage in order to break extra gauge symmetries. Finally, we find that the
mechanism for generating a ``$\mu $-term'' by the K\"ahler potential, as
naturally implemented in orbifolds, leads to the prediction $|tg\beta |=1$ at
the String scale, independently of the Goldstino direction. In this connection,
it is worth noticing that in the dilaton-dominated case we obtain the
remarkable result that the whole SUSY spectrum is completely determined with no
free parameters.
