  We propose a simple method for constructing representations of
(super)conformal and nonlinear W-type algebras in terms of their subalgebras
and corresponding Nambu-Goldstone fields. We apply it to N=2 and N=1
superconformal algebras and describe in this way various embeddings of strings
and superstrings for which these algebras and their subalgebras define
world-sheet symmetries. Besides reproducing the known examples, we present some
new ones, in particular an embedding of the bosonic string with additional U(1)
affine symmetry into N=2 superstring. We also apply our method to the nonlinear
$W_3^{(2)}$ algebra and demonstrate that the linearization procedure worked out
for it some time ago gets a natural interpretation as a kind of string
embedding. All these embeddings include the critical ones as particular cases.
